Question

1.

A ray of light passes from one substance (n₁) into another (n₂). In the scenario where n₁ < n₂, what is the relationship between the speed of light at n₁ with respect to the speed of light at n₂?

greater than

equal to

less than

n/a

2.

When a ray of light hits a flat mirror, what is the relationship between the angle of incidence to the angle of reflection?

greater than

equal to

less than

dependent upon n

3.

Which of the following statements is true?

Laser light is monochromatic

Laser light is coherent

All of the above

None of the above

4. Rank the colors from longest wavelength to shortest wavelength:

Violet, green, red

Blue, red, green

Red, green, blue

Green, violet, red

Red, blue, green

Answer 1

1. First option is the correct one i.e. "greater than".

We know that, refractive index of medium = (speed of light in vacuum)/(speed of light in medium). So, refractive index is inversely proportional to the speed of light in the medium (substance). Since n1 < n2, therefore speed of light will be greater in the first medium (substance) than the second medium (substance). Hence, first option is correct.

2. Second option is correct i.e. "equal to".

According to the law of reflection, the incident ray and the reflected ray make equal angles with the normal to the interface and all the three i.e. the incident ray, reflected ray and the normal lie on the same plane. So, second option is correct here.

3. Third option is correct i.e. "All of the above".

The light produced by a laser light is of single wavelength, meaning light with "one colour", hence laser light is monochromatic. Whereas ordinary light like white light constitutes of many wavelengths making it to be not monochromatic. So, first option is true.

The waves of the laser light are in phase with each other i.e. the waves don't have any phase difference. Therefore, laser light is coherent. So, second option is also true.

Hence third option is the correct choice.

4. Third option is correct i.e. "Red, green, blue".

The wavelength order from shortest to longest is VIBGYOR i.e. Violet<Indigo<Blue<Green<Yellow<Orange<Red. So, red has longest wavelength, then green and then blue. So, third option is correct.