What do you understand by the term 'Scattering of light'? Which colour of white light is scattered the least and why?

(i) Name the waves used for echo depth sounding.

(ii) Give one reason for their use for the above purpose.

(iii) Why are the waves mentioned by you not audible to us?

A copper vessel of mass 100 g contains 150 g of water at 50 °C. How much ice is needed to cool it to 5 °C?

Given : Specific heat capacity of copper = 0.4 J g^-1 ⁰C^-1

Specific heat capacity of water = 4.2 J g^-1 ⁰C^-1

Specific latent heat of fusion of ice = 336 J g^-1

(i) Write a relationship between angle of incidence and angle of refraction for a given pair of media.

(ii) When a ray of light enters from one medium to another having different optical densities it bends. Why does this phenomenon occur?

(iii) Write one condition where it does not bend when entering a medium of different optical density.