Optics (Physics) Part-I

The speed of light in a vacuum is 3.00 × 10⁸ m/s, while the speed of sound in vacuum is zero and in air is 343 m/sec. The speed of light in glass is 2.0 × 10⁸ m/s. The velocity of light always greater than the velocity of sound. The velocity of celestial objects and the rockets is quite low than the velocity of light.

The speed of light in a vacuum is 3.00 × 10⁸ m/s, while the speed of sound in vacuum is zero and in air is 343 m/sec. The speed of light in glass is 2.0 × 10⁸ m/s. The velocity of light always greater than the velocity of sound. The velocity of celestial objects and the rockets is quite low than the velocity of light.

The speed of light depends on the optical density of the (transparent) medium in which it is travelling. The optical density of a medium is not the same as its physical density (which refers to the mass/volume ratio). The refractive index is the indicator of optical density of the medium.

The optical density of air depends on its temperature, pressure and humidity. Hence, the speed of light in air depends on its optical density, temperature and pressure. Atmospheric refraction (e.g. mirage) happens due to change in these gradients.

The speed of light in a vacuum is maximum (c = 3 × 10 ⁸ms⁻¹). The speed of light decreases gradually in optically denser mediums like water or glass. It is least in diamond.

The speed of light in a vacuum is maximum (c = 3 × 10 ⁸ms⁻¹). The speed of light decreases gradually in optically denser mediums like water or glass. It is least in diamond.

Any of the object or material which has the highest refractive index has the minimum speed of light. The glass has the highest refractive index among the given options. Hence, among the given options, the speed of light will be minimum while passing through glass.

The sunlight takes about 499 second or about 8.3 minutes to reach to the Earth. Thus, option (c) is the right answer.

The sunlight takes about 499 second or about 8.3 minutes to reach to the Earth. Thus, option (c) is the right answer.

The sunlight takes about 499 second or about 8.3 minutes to reach to the Earth. Thus, option (c) is the right answer.

Nothing can travel faster than the speed of light. The light waves can travel through a vacuum. The sound waves can not travel through a vacuum. The speed of light is maximum in a vacuum.

Most galactic cosmic rays have energies between 100 MeV (corresponding to velocity for protons of 43% of the speed of light) and 10 GeV (corresponding to 99.6% of the speed of light). The speed of highest energy cosmic rays could be extremely close to but still below, the speed of light in a vacuum.