Advertisements
Advertisements
प्रश्न
What is the speed of light in vacuum?
Advertisements
उत्तर
The speed of light in vacuum is known to be almost exactly 300,000 km per second. In 1665 the Danish astronomer Ole Roemer first estimated the speed of light by observing one of the twelve moons of the planet Jupiter.
APPEARS IN
संबंधित प्रश्न
State whether light slows down or speeds up in the following cases :
Light going from water to air.
A light ray suffers reflection and refraction at the boundary in passing from air to water. Draw a neat labelled ray diagram to show it.
The speed of light in air is 3 × 108 m s-1. Calculate the speed of light in glass. The refractive index of glass is 1.5.
An obliquely incident light ray bends at the surface due to a change in speed when passing from one medium to another. The ray does not bend when it is incident normally. Will the ray have a different speed in the other medium?
Compare the speeds of light of wavelength 4000 Å (i.e. violet light) and 8000 Å (i.e. red light) in vacuum.
Numerical problem.
Light enters from air into a glass plate having refractive index 1.5. What is the speed of light in glass? (Ans: 2 × 108 ms–1)
Materials that allow light to pass through completely are known as ______ material.
Objects that allow light to pass through partially are called ______ material.
Define opaque material.
Light travels a distance of '10x' units in time 't1' in vacuum and it travels a distance of 'x' units in time 't2' in a denser medium. Using this information answer the question that follows:
'Light covers a distance of '20x' units in time 't1' in diamond'. State true or false.
