Lakhmir singh solutions science class 8 Solutions for Chapter 16 light

Exercises in Chapter 16 light Grade 8

Exercise

Questions in Exercise

What is meant by 'incident ray'?

What is meant by 'reflected ray'?

How many reflected rays can there be for a given single incident ray falling on a plane mirror?

What do you understand by the term 'point of incidence'?

What is 'normal' in the reflection of light from a plane mirror?

Define the angle of incidence.

Define the angle of reflection.

A ray of light is incident on a plane mirror at an angle of 30°. What is the angle of reflection?

An incident ray makes an angle of 75° with the surface of a plane mirror. What will be the angle of reflection?

A ray of light is incident normally (perpendicularly) on a plane mirror. Where will this ray of does light go after reflection from the mirror?

What is the angle of incidence when a ray of light is incident normally on a plane mirror?

What is the angle of reflection when a ray of light is incident normally on a plane mirror?

What is the angle of incidence of a ray of light if the reflected ray is at an angle of 90° to the incident ray?

Name the apparatus which is used to obtain a thin beam of light.

What type of reflection of light takes place from:

(a) A rough surface?

(b) A smooth surface?

Which type of reflection of light, regular reflection or diffuse reflection, leads to the formation of images?

What type of reflection of light takes place from?

(a) A cinema screen?

(b) A plane mirror?

If an object is placed at a distance of 7.5 cm from a plane mirror, how far would it be from its image?

Is the image of an object in a plane mirror: virtual or real?

Name the phenomenon responsible for the following effect:

When we sit in front of a plane mirror and write with our right hand, it appears in the mirror that we are writing with the left hand.

Name a device which works on the reflection of reflected light.

How are the two plane mirrors in a periscope arranged?

(a) With respect to one another?

(b) With respect to the sides of the tube?

What will be the number of images formed when an object is placed between two parallel does plane mirror facing each other?

Name an instrument or toy which works by producing multiple reflections from three plane mirrors to form beautiful patterns.

State one use of kaleidoscope.

Name the device used to split white light into seven colours.

What happens when a beam of sunlight is passed through a glass prism?

What type of lens (convex or concave) is present in the human eye?

What is the range of vision of a normal human eye?

Name the point inside the human eye where the image is not visible.

Name the phenomenon which enables us to see movies in a cinema hall.

Name an eye ailment (or eye-disease) caused by the deficiency of vitamin A in the diet.

What is the name of the transparent front part of an eye?

What is the name of a small opening in the iris of an eye?

Which part of the eye gives it its distinctive colour?

Write the names of the main parts of the human eye.

What happens to the size of the pupil of our eye in dim light?

What happens to the size of the pupil of our eye in bright light?

State whether the following statements are true or false:

(a) A moon is an illuminated object.

(b) Diffuse reflection means the failure of the laws of reflection of light.

Fill in the following blanks with suitable words:

(a) The angle of _______ equals the angle of reflection.

(b) A person 1 m in front of a plane mirror seems to be _______ m away from his image.

(c) If you touch your _______ ear with the right hand in front of a plane mirror, it will be seen in the mirror that your right ear is touched with _______

(d) The size of the pupil becomes _______ when you see in dim light.

(e) Night birds have _______ cones than rods in their eyes.

(f) The image of an object persists on the retina of an eye for about _______ second even after the object has disappeared.

(g) If the still pictures of a moving object are flashed on our eyes at a rate faster than _______ pictures per second, the eye perceives the object as moving.

(h) In a movie, the still pictures in the proper sequence are projected on the screen usually at the rate of _______ pictures per second.

Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.

What makes things visible to us? Why cannot we see a book which is placed (a) behind a wooden screen, and (b) in a dark room?

We can see the sun because it is glowing. How are we able to see the moon?

Name the two types of reflection of light. Which type of reflection makes us see an object from all directions?

A wall reflects light and a mirror also reflects light. What difference is there in the way they reflect light?

Explain why a book lying on a table in a room can be seen from all the parts of the room.

What is the full form of $and ? What is the relation between them?$

Do you see your image in a plane mirror? State two characteristics of the image so formed.

What is a periscope? How many mirrors are there is a periscope?

State the various uses of a periscope.

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Chapters in this book

Crop Production And Management

Microorganisms: Friends and Foe

Synthetic Fibres And Plastics

Materials: Metals and Non-Metals

Coal And Petroleum

Combustion And Flame

Conservation Of Plants And Animals

Cell Structure And Its Functions

Reproduction In Animals

Reaching The Age Of Adolescence

Force and Pressure

Friction

Sound

Chemical Effect Of Electric Current

Some Natural Phenomena

Light

Stars And The Solar System

Pollution Of Air And Water