CHAPTER: Light Class 8

1. Write the properties of light.

Ans: Properties of light

i) It is a ray

ii) Rectilinear propagation

2. What is the reflection of light?

Ans: Reverse of light from the surface into the same medium is known as the reflection of light.

3. Write the laws of reflection.

Ans: Law 1. The angle of incidence is equal to angle of reflection (<i = <r).

Law 2. Incident ray, reflected ray, normal and point of incidence all lie in same plane.

4. Draw the diagram of the reflection of light.

Ans:

5. What is reflecting surface?

Ans: Smooth shiny surface that reflects light is called reflecting surface.

6. What is Incident ray?

Ans: Ray of light which falls on reflecting surface is called Incident ray.

7. What is Point of incidence.

Ans: The point where incident ray fall on the reflecting surface is known as Point of incidence.

8. What is Normal?

Ans: It is a perpendicular ( imaginary) line on the reflecting surface at point of incidence.

9. What is Angle of incidence?

Ans: The angle between the incident ray and the normal is known as the Angle of incidence. It is denoted by ''i''.

10. What is Angle of reflection?

Ans: The angle between normal and reflected ray is known as Angle of reflection.

11. Write the difference between regular reflection and irregular reflection.

Ans.

Regular reflection	Irregular reflection
Plane surface	Rough surface
Reflected parallel	Reflected different direction

12. Why are used rough screens instead of plain surfaces in Cinema Hall?

Ans: Rough surface reflects defuse reflections so all the spectators can see the program. If we use plain surfaces then some spectators can not see the program for regular reflection.

13. Define Plane Mirror.

Ans: A Plane Mirror made of thin glass whose one side silvering or polishing.

14. Write the properties of the Real Image.

Ans: i) On-screen

ii) Inverted

iii) Same or smaller or bigger in size

15. Write the properties of virtual image.

Ans: i) Behind the mirror

ii) Erect

iii) Same or smaller or bigger in size.

16. What is Lateral Inversion?

Ans: Sidewise reflection on the mirror is called Lateral Inversion.

17. Write the characters of image formed by the plane mirror.

Ans: i) Inverted

ii) Same size

iii) Behind the mirror ( virtual )

iv) Same distance between the object to mirror and mirror to image.

18. Write about the Dispersion of Light.

Ans: Splitting of white light into seven different colours ( VIBGYOR ) is called Dispersion of Light.

19. Write about Primary Colour.

Ans: Red, Green, and Blue colours are called Primary Colours because we can not create these colours by mixing.

20. Write about Secondary Colour.

Ans: Secondary colours are created by mixing primary colours.

Example - Yellow = Red + Green

Cyan = Blue + Green

Magenta = Red + Blue

21. Give examples of Subtraction of colour.

Ans: i) White - Green = Red + Green + Blue - Green

= Red + Blue

= Magenta

ii) Yellow - Red = Red + Green - Red

= Green

22. 'A green leaf is seen in red light' - which colours is appeared and why?

Ans: It appears in dark ( black ).

Reason - Green leaf absorb the red colour, no colour is reflected so it appears in dark.

23. Which colour will be formed in the blank place?

Ans: Yellow colour will be formed because yellow colour is secondary colour. It is formed on mixing red and green colours.

24. Which colour will be formed in the blank place?

Ans: Cyan colour is present in the blank area. So, the green and blue colour is reflected by the oval surface and the red colour is absorbed.

25. What is the speed of light in the air?

Ans: The speed of light in air is 3 × 10⁸ m / s.

26. Write the laws of refraction.

Ans: First Law - The incident ray, the refracted ray and the normal to the refracting surface all lie on the same plane.

Second Law - Sin i / Sin r = Constant ( μ )

Tags with: ICSE Chapter Light Class 8, ICSE Science Class 8, ICSE and CBSE Class 8 Solutions, Chapter: Light Class- 8, ICSE Science Class - 8, Science Class - 8, ISCE-CBSE- Science Class - 8 Solutions, ICSE Class 8 Solutions.