7th Std Science Lesson Wise Questions in English – Part 2

7th Science Lesson 12 Questions in English

12] Light

1. What is the main source of energy for the plants?

a) Light energy

b) Water

c) Soil

d) Atmosphere

Explanation

Light is the only source of energy for plants. So they entirely depend on light.

2. Which is not organic plant based energy for people and animals?

a) Carbohydrates

b) Protein

c) Minerals

d) Fat

Explanation

People and animals derive energy from carbohydrates, protein and fat through their food.

3. Which of these are used to produce energy in photosynthesis?

a) Carbon-di-oxide

b) Sun light

c) Water

d) All the above

Explanation

Plants produce food using the energy from Sun light, carbon-di-oxide and water by the process called as Photosynthesis. Sun light acts a vital role in the process of photosynthesis.

4. Assertion (A): Light sources are objects that can emit light.

Reasoning(R): Sun is the only source of light rays.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Objects which are able to emit light are known as light sources. Light rays can come from different sources.

5. How many sources of light are categorized?

a) 3

b) 2

c) 4

d) 1

Explanation

There are two types of sources of light, natural sources of light and artificial sources of light.

6. Assertion (A): The Sun is the primary source of natural light.

Reasoning(R): The natural sources of light emit naturally.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Sources which emit light naturally are known as natural sources of light. The Sun is the primary and the major source of natural light.

7. Which of these results in the weak star light?

a) Huge distance from sun

b) Weak luminescence of stars

c) Atmospheric dust

d) All the above

Explanation

Stars also produce light in the same way as the Sun do. However as they are much farther away than the Sun the light from them are too weak.

8. Which of these refers to the ability of living organisms producing light?

a) Bioluminescence

b) Crystalloluminescence

c) Mechanoluminescence

d) Electroluminescence

Explanation

Some living organisms have the ability to produce light named by bioluminescence. It is the effect of certain chemical reactions occurring in the organism.

9. Which of these does not emit light naturally?

a) Jellyfish

b) Glow worm

c) Moon

d) Fireflies

Explanation

Fireflies, jellyfish, glow worm, certain deep sea plants and some microorganisms can emit light naturally.

10. How many artificial light sources are classified?

a) 4

b) 7

c) 3

d) 5

Explanation

The different light sources that are able to produce light artificially can be put under three broad categories.

11. Choose the incorrect statements regarding properties of the moon.

i) It cannot produce light on its own.

ii) The light of sun is reflected by the moon.

iii) The whole part of moon is faced by earth.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

The moon provides light as well but it cannot produce light by its own. The light emitted by the Moon is the light of the Sun reflected towards the Earth. When we see the Moon we see only the Moon’s lighted part. Thus half of the moon is always facing the Sun and receiving light from it. Hence, we receive light from the moon.

12. Assertion (A): All the man made light sources is categorized as the artificial sources of light.

Reasoning(R): Neon lamp is an artificial light source.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Artificial sources are man – made light sources such as flame of candle, incandescent lamp, neon lamp, Sodium lamp etc.

13. Which of these used to produce light in incandescent sources?

a) High temperature

b) Low pressure

c) High intensity

d) Low energy

Explanation

Incandescent Sources: When certain objects are heated to a high temperature, they begin to emit light. The glowing of hot iron rod is a kind of Incandescent light. Example: Candle, incandescent lamp.

14. Which of these are not related to the gas discharge sources of light?

a) Low pressure gas

b) Electricity

c) Candle

d) Neon lamp

Explanation

Gas Discharge Sources: Passing electricity through certain gases at a very low pressure (discharging) can produce light. Example: Neon lamp, Sodium lamp

15. Which of these is used to excite the gas in a gas discharge lamp?

a) Electric current

b) Pressure variation

c) Sun light

d) Chemical reactions

Explanation

We often use a kind of gas discharge lamp that uses fluorescence to produce visible light. The electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow in visible light.

16. Which of the following is not a fundamental property of light energy?

a) Reflection

b) Speed

c) Non-transverse

d) Spectrum

Explanation

Light has some fundamental properties which are rectilinear propagation of light, Reflection, Speed, Interaction of light with matter and Spectrum.

17. Which of this property describes the interaction of light with matters?

a) Permeability of materials

b) Shadow formation

c) Plane mirror and images

d) All the above

Explanation

Interaction of light with matter describes the types of material according to permeability, Formation of shadows and Plane mirror and images.

18. What is the most important property of light?

a) Light travels through objects.

b) Light travels faster than sound.

c) Light travels in straight line.

d) Light is the secondary source of energy.

Explanation

Light travels in straight line it cannot bend the path itself. This is called as the rectilinear propagation of light. This is one of the most important properties of light.

19. Which of this light property was experimented by Al-hasan-Haytham?

a) Rectilinear propagation

b) Spectrum

c) Shadow

d) Plane of incidence

Explanation

Al-hasan -Haytham was a scientific thinker who made important contribution to the understanding of vision optics and light. He is the first one to experiment with light and found important properties like the rectilinear propagation of light.

20. Name the type of photography which used the pinhole camera to capture the movement of the sun?

a) Solography

b) Macro photography

c) Motion photography

d) Tilt-shift photography

Explanation

Before the advancement of camera Pinhole camera was used to photograph movement of the sun over a long period of time. This type of photography is known as solography and also be used for observing and recording solar eclipses. And it was also used to take photograph of stationary objects.

21. Which is referred as the light falling on the mirror or surface?

a) Incident ray

b) Direct ray

c) Indirect ray

d) Bundle rays

Explanation

The light falling on the mirror is called as incident ray and the light reflected is called reflected ray.

22. Choose the correct statements.

i) The angle of incidence is always equal to the angle of reflection.

ii) The incident ray and the reflected ray lie on different planes.

a) i only

b) ii only

c) Both i and ii

d) None of the above

Explanation

Laws of reflection: The angle of incidence is always equal to the angle of reflection. i = r. The incident ray, reflected ray and the normal at the point of incidence lie on the same plane.

23. Which is referred as the angle of reflection?

a) Angle between normal and reflected ray.

b) Angle between incident ray and reflected ray.

c) Angle between Angle of incidence and reflected surface.

d) Angle between Angle of incidence and normal angle.

Explanation

24. Find the angle of incidence for a light ray striking a reflective plane surface at an angle of 72° with the plane surface?

a) 18°

b) 90°

c) 72°

d) 81°

Explanation

Solution: Angle of incidence, i = 90 -72 = 18°

Angle of reflection, r = i = 18°

25. In which of these surfaces the law of reflection is good?

a) Vertical surface

b) Angled surface

c) Curved surface

d) All the above

Explanation

The laws of reflection holds good for all surfaces irrespective of the shape. Vertical surfaces, angled surfaces and even over the curved surfaces, the laws of reflection holds good.

26. On which of this condition the angle of incidence and reflection are equal?

a) Normal is perpendicular to surface.

b) Surface is smoother.

c) Reflective surface is mirror.

d) None of the above

Explanation

As long as we can draw the normal perpendicular to the surface at the point can be drawn the angle of incidence at that point will be equal to angle of reflection.

27. Choose the correct statements.

i) The surface orientation influences the law of reflection.

ii) Smooth surfaces have normal in the same direction at all points.

iii) The parallel rays striking the surface will be reflected at various angles.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

The law of reflection is always observed regardless of the orientation of the surface. If the surface is smooth, and flat all points on it have the normal in the same direction. Therefore a set of parallel rays striking the surface will be reflected at an angle but the rays themselves will still remain parallel to each other.

28. How many types of reflection are categorized based on the surface?

a) 2

b) 4

c) 5

d) 3

Explanation

Broadly we can say that there are two types of reflection. If the surface is smooth then we have specular reflection. The parallel light rays striking the surface gets reflected yet individual reflected rays remain parallel.

29. Which of these surface results in diffused reflection?

a) Rough surface

b) Curved surface

c) Smooth surface

d) Plane surface

Explanation

If the surface is rough then we have diffused reflection. Light rays after reflection go in many directions.

30. Assertion (A): Light is a single ray called as a beam of light.

Reasoning(R): A light beam is a bundle of divergent rays.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Generally light is not a single ray but a bundle of rays which are called as a beam of light. A light beam can be a bundle of parallel rays’ convergent rays or divergent rays.

31. Choose the Incorrect statements.

i) The Sunlight rays are parallel.

ii) Light rays from a candle are in all directions.

iii) Flash light rays are parallel rays.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

The rays of sunlight are parallel. Often the headlight of car gives parallel rays. However look at the rays of light coming out of a candle. Light rays go in all directions, from the candle fire. These rays are divergent. Light rays from a flash light are also divergent.

32. Choose the correct statements.

i) Lenses are used for converging the light rays.

ii) Sunlight cannot be converged by using a lens.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Using lenses we can converge light rays. Using a lens you can focus sunlight at a point. That is what we are making the light rays to converge.

33. Assertion (A): Light travels faster than the sound.

Reasoning(R): Theoretically nothing can travel faster than light.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

When lighting a bulb in a dark room light spreads the whole room quickly. This is because the light travels very fast. In theory nothing can travel faster than light.

34. Which of this unit is used to measure the speed of light in air?

a) Kilometer per hour

b) Meter per second

c) Kilometer per second

d) Meter per hour

Explanation

Light travels three lakh kilometers per second in air or vacuum.

35. How many materials are classified based on the permeability?

a) 5

b) 3

c) 7

d) 4

Explanation

Depending upon permeability materials can be classified into three categories.

36. Identify the incorrect Match.

A. Transparent material i) Eye glasses

B. Opaque material ii) Stone

C. Translucent material iii) Card board

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

Transparent Material: Eye glasses, clear drinking glass, clear water, face glasses used in buses.

Translucent Material, Opaque Material: Wall, thick card board, stone, etc

37. Which of these statements are not true regarding the concept of shadows?

a) Shadow is caused by the rectilinear property of light.

b) Shadow is always against the opposite side of the light source.

c) Only some of the opaque objects stop light propagation.

d) Shadow consists of both umbra and penumbra.

Explanation

Light travels in a straight line. Hence it cannot go around such objects. That is why we see shadow. Shadow is always against, opposite side of light source. It is caused by opaque objects that stop light from propagating.

38. Assertion (A): The uniform dark shadow of an object appearing on screen is called as umbra.

Reasoning(R): A shadow will be formed when an opaque object is placed in the path of light source.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

When an opaque object is placed in the path of light from a point source a uniform dark shadow will appear on the screen. This is shadow is called as umbra.

39. Which is the illuminated shadow part of an object placed in the path of light?

a) Penumbra

b) Umbra

c) Darkest part

d) Shadow line

Explanation

When an opaque object is placed in the path of light coming from a broad source of light a small umbra will appear on the screen and an illuminated shadow area appears around umbra. This illuminated shadow area is called as penumbra.

40. Choose the incorrect statements.

i) The Umbra is the darkest part of a shadow.

ii) The umbra always surrounds the penumbra.

iii) Light rays are completely prevented by the opaque object in umbra part.

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

The penumbra always surrounds the umbra. The umbra is the darkest part of a shadow. In this part light rays are completely prevented by the opaque object. The lighter shade of shadow is the penumbra.

41. Which of the following does not fall under the properties of shadow?

a) Every object will form shadow.

b) Shadows will be formed in the opposite side of light source.

c) Shadows are always darker.

d) Opaque objects only form shadows.

Explanation

Properties of shadow: All objects do not form shadows. Only opaque objects form shadows. Shadows will be formed in the opposite side of light source. It cannot be determined the characteristics of an object by its shadow. The shadow will be always darker whatever may be the color of light rays.

42. Which of these factors decide the size of the shadow?

a) Distance between light source and object.

b) Intensity of the light source.

c) Color of the light rays.

d) Characteristics of the object.

Explanation

Light source, opaque object are shadow all are in a straight line. The size of shadow depends upon the distance between light source and object and the distance between object and the screen.

43. Assertion (A): Eclipse is an incident when any astronomical object is partially or fully obscured in the presence of light.

Reasoning(R): Solar and lunar eclipse occurs due to the property of rectilinear propagation of light.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

An eclipse is an incident when any astronomical object is partially or fully obscured due to the placement of another astronomical object in the presence of light. Thus solar and lunar eclipses are occurring that are due to the property of light known as the rectilinear propagation of light.

44. Choose the correct statements.

i) Solar eclipse occurs if earth arrives between the moon and the sun.

ii) The shadow of the earth appears on the moon.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Solar eclipse occurs, when the moon arrives between the sun (S) and the earth (E). The shadow of the moon appears on the earth at A as shown in picture. Hence those who are at the region A are unable to see the Sun instantly. This is solar eclipse.

45. Which of this prevents the light in the lunar eclipse?

a) Moon

b) Earth

c) Sun

d) All the above

Explanation

Lunar eclipse: Lunar eclipse occurs, when the earth (E) comes between the sun (S) and the moon (M). The earth prevents light coming from the sun and makes shadow on the moon. This is lunar eclipse

46. What is the relation between the distance of object (a) and image(b) from the mirror?

a) a > b

b) a < b

c) a = b

d) a + b

Explanation

­The distance of the object from the mirror is equal to the distance of the image from the mirror (a=b).

47. Assertion (A): Optical fiber transmits huge data with negligible loss of energy in short time.

Reasoning(R): Optical fibers works on the total internal reflection of light signals.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Optical fiber is a device that works on the principle of total internal reflection by which light signals (huge data) can be transmitted from one place to another place with a negligible loss of energy in a very short time.

48. Assertion (A): Optical fibers can be easily twisted and bent.

Reasoning(R): Optical fibers consist of thin flexible fibers with a glass core.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Optical fiber consists of a cable having one or more thin flexible fibers with a glass core through which light signals can be sent. Optical fiber can be twisted and bent easily.

49. Choose the Incorrect statements.

i) Optical fibers are used for high speed communications.

ii) Fiber optics carries fewer signals than traditional copper cable lines.

iii) Cable television and high speed broad band services uses the optical fibers for communication.

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

Optical fibers have become very important in high-speed communications, such as cable TV and high-speed broadband services. Fiber optic cables are able to carry more signals than traditional copper cable telephone lines.

50. Choose the correct statements.

i) The real image is obtained on a screen.

ii) Virtual image cannot be obtained on a screen.

iii) Image on pinhole camera is upside down.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

The images that are obtained on a screen are called ‘real image’ and that which cannot be obtained on a screen ‘virtual image’. The image on pinhole camera was upside down. The mirror image was upright.

51. Which of these properties of image formation is not true for a plane mirror?

a) Image formed is upright.

b) Virtual image is formed in the plane mirror.

c) Image is slightly small than the object.

d) Image is laterally inverted.

Explanation

Properties of Image formed in a plane mirror: Image formed in a plane mirror is upright, Image formed in a plane mirror is virtual, the image is of the same size as the object. The distance of the image from the plane mirror is equal to the distance of the object from the mirror, Image is laterally inverted.

52. Which human part is stimulated by the light energy?

a) Retina

b) Cell

c) Nerves

d) Skin

Explanation

Color of sunlight : Light is a form of energy in the form of a wave that simulates that retina of our eyes.

53. What range of wavelength is represents the visible light spectrum?

a) Nano meter

b) Micro meter

c) Centimeter

d) Millimeter

Explanation

Visible light is a spectrum of a number of waves with different wavelength range from 400nm to 700nm (1nm = 10-9 meter) each wave has a definite wavelength represents a particular color.

54. Which of the following color is not in the band of visible light?

a) Pink

b) Yellow

c) Orange

d) Blue

Explanation

The band of visible light is VIBGYOR.

55. Which of this color has the shortest wavelength?

a) Green

b) Violet

c) Red

d) Magenta

Explanation

Violet color has shorter wavelength and red color has longer wavelength.

56. Choose the correct statements.

i) White is the combination of all the colors of the visible light.

ii) Black color observes all the wavelength of visible light.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

White is not a color at all. But it is the combination of all the colors of the visible light spectrum. If the entire wavelength (colors) of visible light spectrum give appearance of white similarly the observe of all there wavelength of visible light will lead appearance of black.

57. Which of these statements are not true regarding the concept of Prism?

a) Prism is made up of transparent material.

b) It has more than three flat surfaces.

c) The flat surfaces of prism forms an acute angle.

d) Plastic and glass are used to construct a prism.

Explanation

A prism is an object made up of a transparent material like glass or plastic that has at least two flat surfaces that from an acute angle (less than 90 degrees).

58. Why is the word “AMBULANCE” written backwards in ambulance vehicle?

a) Lateral inversion

b) Plane of incidence

c) Total reflection

d) Internal reflection

Explanation

This is due to lateral inversion .The phenomenon due to which the left side of an object appears to be right side of the object in its image in a reflecting medium (mirror) so that drivers see the word the right way around in their rear-view mirror.

59. Choose the Incorrect statements.

i) Real images are formed by the pinhole camera.

ii) The plane mirror images are erected one.

iii) The images formed by the pin hole camera is equal to the size of the object.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Difference between the images formed in Pinhole camera and Plane mirror

60. Assertion (A): Red color can travel a longest distance even through air and fog.

Reasoning(R): Red color has the highest wavelength of all the colors.

a) Both A and R is True and R is the correct explanation of A.

b) Both A and R is True but R is not the correct explanation of A.

c) A is True but R is False.

d) Both A and R is False.

Explanation

Red color is scattered the least by air molecules. Red color has the highest wavelength of all the other colors. So, red color is able to travel the longest distance through air, fog.

61. Which of these colors forms a rainbow in a prism?

a) White

b) Red

c) Black

d) Green

Explanation

When white light is passed through a prism as shown in the figure the colors of the rainbow emerge from the prism.

62. Choose the Incorrect statements regarding the Newton Disc.

i) It has seven unequal colored sectors.

ii) Human retina receives the whole disc spectrum simultaneously and disc appears white.

iii) White is a combination of VIBGYOR.

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

Newton Disc is a card board disc with seven equal sectors colored red, yellow, orange, green, blue, indigo and violet. When the disc turned quickly the retina receives the sensation of the spectrum simultaneously and disc appears white. Using this disc one can explain that white is a combination of VIBGYOR.

63. Which of these is defined as synthesis of color?

a) Creating color by mixing various proportions of colors of light.

b) Differentiating primary and secondary color.

c) Light experiment of various colors.

d) Creating light by various colors.

Explanation

Synthesis of color is the method of creating color by mixing various proportion of two (or) three distinct colors of light.

64. Which of these are categorized as primary colors?

a) Red

b) Green

c) Blue

d) All the above

Explanation

The distinct colors are Red, Green and Blue called as primary colors.

65. Which of these is not a secondary color?

a) Magenta

b) White

c) Cyan

d) Yellow

Explanation

Equal proportions of two primary color create a secondary color. Magenta, Cyan and yellow are called secondary color. Equal proportions of all three primary color create white.