Physics - Study Mode

[#1191] A light ray travelling from denser to rarer medium at an angle of incidence more than critical angle of concerned media pair suffers.
Correct Answer

(D) Total internal reflection

Explanation

Solution: If the angle of incidence of light ray in the denser medium is greater than the critical angle of the concerned media pair, the light is not at all reflected in to the rarer medium but is totally reflected. This is known as 'total internal reflection'.

[#1192] The snow on the mountains does not melt all at once when it is heated by the sun because:
Correct Answer

(B) It reflects most of the heat from the sun

Explanation

Solution: Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. It melts because of the warm air from the sea.

[#1193] Cloudy nights are warmer compared to clear cloudless nights, because clouds mainly
Correct Answer

(C) Reflect back the heat given by earth

Explanation

Solution: It is because the night side of Earth will radiate infra-red radiation (heat) back into space. When there is cloud cover, the clouds act like a blanket and trap the heat close to the ground just like a blanket traps heat close to our body.

[#1194] In which one of the following the phenomenon of total internal reflection of light is used ?
Correct Answer

(A) Formation of mirage

Explanation

Solution: Formation of mirage is the phenomenon of total internal reflection of light.

[#1195] Which type of mirror is used in the head lights of vehicles ?
Correct Answer

(B) Concave mirror

Explanation

Solution: Concave mirrors are used in head lights of vehicles because when the bulb of headlight is placed at focus of concave mirror it will allow the light to spread out to infinity after the reflection on the mirror.