SKJ_ProbMat

Front

What is a phosphor?

Back

A phosphor is a substance that emits light when excited by radiation, typically converting high-energy photons to low-energy photons.

Front

What is the refractive index of a material?

Back

The refractive index is a dimensionless number that describes how light propagates through that medium, determined mainly by the material's dipoles.

Front

What happens to photons with energy below the band gap in a semiconductor photodetector?

Back

They are mostly transmitted without absorption.

Front

What is the formula for phase velocity when a wave travels from vacuum into a non-magnetic medium?

Back

The phase velocity is given by c/n, where c is the speed of light in vacuum and n is the refractive index.

Front

Which material has the highest refractive index and why?

Back

Diamond has the highest refractive index due to its lattice having a very high atomic concentration.

Front

What is the role of dipoles in determining the refractive index of a transparent medium?

Back

Dipoles in the material interact with the electric field of light, affecting how light is refracted.

Front

What is the relationship between phase velocity and group velocity in a medium?

Back

In general, phase velocity is not equal to group velocity; they can differ depending on the medium.

Front

What is the significance of the band gap in semiconductors?

Back

The band gap determines the energy required to create electron-hole pairs and affects the absorption of photons.

Front

How does the atomic number of a material influence its refractive index?

Back

Materials with higher atomic numbers tend to have higher refractive indices due to increased electron density.

Front

What is total internal reflection?

Back

Total internal reflection occurs when a wave hits a boundary at an angle greater than the critical angle, causing it to reflect entirely back into the medium.