Question

i) Describe experiments to show that dark-coloured objects are better radiators and better absorbers of radiant heat than light -coloured objects .

ii) Based on this,what advice will you give people about the kind of clothes that should be worn in summer and winter ?

Answer 1

1. Radiation is the heat that is transmitted from one object to another object in straight lines in all directions with a great speed without the aid of particles of the medium.
2. The amount of heat radiated by the body depends upon the temperature, colour and nature of the material.

i) Experiment to show that dark colour objects are better radiators and better absorbers of radiant heat than light coloured objects.

1. Take two cans with tight-fitting lids and make holes in the lids to hold thermometers.
2. Remove the labels and paint the surface of one tin with black paint and leave the other shiny.
3. Now pour equal quantities of boiling water into two tins and note the temperatures on the two thermometers.
4. Note the temperatures again after every five minutes.
5. You will observe that the temperature drop in the tin painted black is greater than in the tin with a shiny surface.
6. This is because a black surface is a good absorber and radiator of heat while a shiny surface is a poor absorber and radiator of heat.
7. The amount of radiant heat received by an object depends on its distance from the source.

ii) Clothes to wear in summer and winter.

1. In summer as it is very hot, it is better to wear light colour clothes because they can reflect the maximum of the heat rays.
2. Light or white colour clothes are the good reflectors of heat and make you feel cool.
3. In winter as the temperature is very low, it is better to wear the clothes which give you a torridity feel, like dark colour clothes.
4. Dark colour clothes are good absorbers of heat and it makes your body feel hot.