Physics Quiz 2

Optical fibre works on the principle of total internal reflection. When light ray strikes at the internal surface of an optical fibre cable called such that incidence angle is greater than critical angle, then incident light ray reflects in the same medium and this phenomenon repeats.

A metal plate with a circular hole at the centre is heated, then the hole will expand in the same ratio as the metal. This is because the metal plate does not expand radially from the hole, it expands along the circumference i.e. the circumference of the ring expands in the same ratio as the width of the plate.

The instrument used to see the distant objects on the Earth is a terrestrial telescope. Astronomical telescopes are used for viewing distant stars and planets whereas terrestrial telescopes are used for viewing distant objects on earth.

Ventilation is mainly used to control indoor air quality, temperature, humidity, and air motion. It is provided near the ceiling of the room because the exhaled warmer air rises up and goes out.

The penetrating power is the amount of energy that is absorbed depending on the type of radiation and the type of absorbing material. Alpha Rays have the least penetrating power as they are massive in nature. Gamma rays are the most penetrating of all the radiations.

When a person walking in bright Sunlight enters a dark room, he is not able to see clearly for a little while because the iris is unable to dilate the pupil immediately.

The sky appears blue when the scattering of light takes place. As there is no atmosphere in space and hence light does not scatter into its constituent colours that is why the sky appears dark instead of blue to an astronaut in space.

Adiabatic demagnetization is a process by which the removal of a magnetic field from certain materials serves to lower their temperature. It comes under magnetic cooling, exploiting paramagnetic properties to cool some materials down.

As altitude increases and atmospheric pressure decreases, the boiling point of water decreases. To compensate for the lower boiling point of water, the cooking time must be increased. Turning up the heat will not help cook food faster.

The air layer between two shirts behaves like insulating media. Air in general is a good thermal insulator, but it can transmit heat through convection. However, if the air pockets inside the insulating material are separated from each other, heat flow from one air pocket to another cannot happen easily.