1.

(a) Define heat capacity and state its SI unit. (b) Why is the base of a cooking pan generally made thick ? (c) A solid of mass 50 g at 150°C is placed in 100 g of water at 11°C, when the final temperature recorded is 20°C. Find the specific heat capacity of the solidfSpecific heat capacity of water – 4.2 J g -1 °C -1 ). (d) How is the refractive index of a material related to : (i) real and apparent depth ? (ii) velocity of light in vacuum or air and the velocity of light in a given medium ? (e) State the conditions required for total internal reflection of light to take place.

Answer»

(a) It is defined as the amount of heat required in raising the temperature of a unit mass of a substance through 1°C. Its SI unit is J kg-1 K-1. 

(b) It is because thicker pans can have better heat distribution and heat retention due to thermal conductivity and thermal mass. 

(c) Given mass of solid ms = 50 x 10-3 kg Mass of water mw = 100 x 10-3 kg

Temperature of solid = 1500°C 

Temperature of water = 110°C 

Final temperature = 200°C 

Specific heat of water = 4.2 J kg-1 °C-1 

Now, heat lost by the solid = heat gained by water 

50 × 10-3 × c × (1500 – 200) = 100 x 10-3 × 4200 × (200 – 110) Or c = 581 J kg-1 °C-1 

(d) (i) μ = real depth/apparent depth

(ii) μ = c/v

(e) (i) The incident ray should travel from the denser to the rarer medium. 

(ii) The angle of incidence in the denser medium should be greater than the critical angle for the given pair of media.


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