Practice MCQ Questions and answers on Physics-GK

Bats can fly in dark because they produce ultrasonic waves. ... It produces ultrasonic waves which strike with the obstacles present on its way.

Sonar (originally an acronym for Sound Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.

The sounds having a frequency of 20 Hertz to 20,000 Hertz are known as audible sounds.

In a spherical mirror, one of the two curved surfaces is coated with a thin layer of silver followed by a coating of red lead oxide paint. Thus, one side of the spherical mirror is opaque and the other side is a highly polished reflecting surface.

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'.

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.

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.

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

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.

If objects appear enlarged and inverted in a rear view mirror, then concave mirror is used.