Test: Light, Shadows & Reflections- 2


25 Questions MCQ Test NCERT Textbooks (Class 6 to Class 12) | Test: Light, Shadows & Reflections- 2


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QUESTION: 1

Mist is a

Solution:

medium which transmits rays of light so diffused that objects cannot be seen distinctly; that is, the medium is only partially transparent. 

QUESTION: 2

Wool is a

Solution:

Objects through which we cannot see are called opaque objects. A medium that does not allow light to pass through it is called an opaque medium.

Examples of opaque medium are a pencil box, wool, a wooden screen, a book, a towel, a ceramic plate and chart paper.

QUESTION: 3

Stars are

Solution:

In order to emit light, the object must have its own source of energy. A torch shines because of the chemical energy stored in its batteries, whereas all stars shine using energy created by nuclear fusion. Sun also emits light as a result of fusion of Hydrogen atoms. Hence they are considered as Luminous objects.

QUESTION: 4

Moons and planets

Solution:

The most reflected body/ moon in our solar system is Enceladus, a moon of Saturn. It reflects about 90% of light that falls on its surface.

QUESTION: 5

Vacuum is a

Solution:

A medium which has the property of transmitting rays of light in such a way that the human eye may see through the medium distinctly is called transparent medium.  As vacuum consists of nothing so light can easily pass through it without being absorbed or reflected . Hence we can also say vacuum is the best and 100% transparent medium.

QUESTION: 6

Rectilinear propagation of light means

Solution:

The rectilinear propagation of light means that light travels in straight lines as a wave. In a pinhole camera, the light rays reflecting from the bottom of the object travel in a straight line through the pinhole to the film.

QUESTION: 7

A non luminous body can be made luminous by

Solution:

A non luminous object can be made luminous by heating it. Take an iron rod & heat it on a gas flame. In about two minutes, the iron wire will get red hot & start emitting light

QUESTION: 8

The speed of light is

Solution:

The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light.

QUESTION: 9

The light from the sun reaches the earth in

Solution:

Sunlight travels at the speed of light. Photons emitted from the surface of the Sun need to travel across the vacuum of space to reach our eyes. The short answer is that it takes sunlight an average of 8 minutes and 20 seconds to travel from the Sun to the Earth.

QUESTION: 10

A body which emits light by itself is

Solution:

Objects that emit light on their own is called as luminous body.

Sun is the best example 

QUESTION: 11

The star which is very bright during early evening

Solution:

It began with Venus

Originally, the terms "morning star" and "evening star" applied only to the brightest planet of all, Venus. Far more dazzling than any of the actual stars in the sky, Venus does not appear to twinkle, but instead glows with a steady, silvery light.

QUESTION: 12

The size of a shadow of an opaque object close to the screen and away from the source of light

Solution:

The size of the shadow of an opaque object close to the screen and away from the source of light, decreases.

QUESTION: 13

This takes place from smooth polished surface when a beam of light falls on it

Solution:

The process through which light rays falling on the surface on an object are sent back is called reflection of light. Thus, when light falls on the surface of an object it sends back the light. The objects having shiny or polished surface reflects more light compared to the objects having dull or unpolished surface.

QUESTION: 14

The image formed in pinhole camera is

Solution:

The image produced by a pinhole camera is usually smaller than the object and appears to be inverted on both the vertical and horizontal axis when compared to the actual object.

QUESTION: 15

An optical medium having uniform composition throughout is

Solution:

homogeneous medium has uniform properties throughout its volume. That is, it does not have lumps of different stuff in it. 

QUESTION: 16

A dark patch formed by an opaque body placed in the path of light is called

Solution:

An opaque object blocking the path of light is called a shadow. A shadow is a dark region, and is formed only when a light source, an opaque object and a screen are present. Opaque objects form shadows because light is not able to bend around them.Shadows are seen more clearly on light screens.

QUESTION: 17

Reflection does not takes place from a

Solution:

Reflection takes place whenever ray of light travels from a transparent medium towards an opaque medium. The opaque medium does not let the light pass through.

QUESTION: 18

The shadow is the dark outline of

Solution:

A shadow is a dark outline or image cast by an opaque object that blocks light coming from a source of light. It is formed when light hits the opaque object which does not let the light pass through it. 

QUESTION: 19

Shadows are formed only when the

Solution:

Shadow has formed when the opaque object comes in the light path because the light travels in the path of straight line and then the “opaque object” obstructs it, shadow is formed.

QUESTION: 20

This screen is a must to receive the shadow

Solution:

The correct option is B.
A shadow is a dark region, and is formed only when a light source, an opaque object and a screen are present. Opaque objects form shadows because light is not able to bend around them.

QUESTION: 21

Luminous objects are objects

Solution:

Objects that emit light on their own are called luminous objects. Best examples of luminous objects are the sun, stars, light bulb etc. Objects that do not reflect light are known as non luminous objects. Examples of non luminous objects are wood, plastics, metals etc.

QUESTION: 22

The smooth polished surface from which reflection takes place is

Solution:

A highly polished surface, such as a mirror, reflects most of the light falling on it. When light falls on the surface of the object, it may be absorbed, transmitted or reflected. If an object absorbs all the light, which falls on it, it will appear perfectly black. If an object transmits the light, that is, if the object allows the light to pass through itself, the object is said to be transparent.

QUESTION: 23

A red hot iron wire starts emitting light, at this time the temperature of the iron is

Solution:

A non luminous object can be made luminous by heating it. Take an iron rod & heat it on a gas flame. In about two minutes, the iron wire will get red hot & start emitting light. At this moment, the temperature of iron is between 600 - 800 degrees Celsius

QUESTION: 24

Shadows are

Solution:

As light moves towards the object, the shadow becomes larger. As light moves away from the object, the shadow becomes smaller. As light moves closer, the shadow becomes longer and wider.

QUESTION: 25

An example for the rectilinear propagation of light is

Solution:

Effects of rectilinear propagation of light:

- Formation of shadow

- Formation of day and night

- Formation of image from a pinhole camera