Question

1. What is absolute refractive index? What is the unit of refractive index?
2. Refractive index of water is 4/3. What is the speed of light in water, if the speed
light in air is 3 x 10 m/s?
3. What do you understand by the term 'optical density' of a medium?
4. Where should an object be kept in front of a convex lens to obtain a virtual and
image?
5. What do you understand by lateral displacement in a rectangular glass slab? Dr
well labelled diagram showing it.
6. State Snell's law of refraction
7. Write (a) Mirror formula (6) Lens formula
8. What is the power of a lens? Find the focal length of a lens of power -2D. Ident
the type of lens.
9. A concave lens of focal length 15cm forms an image 10cm from the lens. How!
the object placed from the lens?
10. Draw a ray diagram to show the position of the image for : (a) a concave mirrc
when object is placed between F and C (b) a convex lens when the object is pla
beyond 2F​

Answer 1

Q.2.

Given: retractive index of water = 4/3

speed of light in vacuum= 3×10^8m/s = c

speed of light in water = v

Using,

refractive index of water = c/v

v = c/refractive

index of water

v = (3×10^8/4) × 1/3

= 10^8/4

= 25 × 10^6

Therefore, speed of light in water is 25 × 10^6m/s.