Refraction — Set 1
Physics · अपवर्तन · Questions 1–10 of 70
What is refraction of light?
Correct Answer: B. Bending of light due to change in speed in a new medium
Refraction is the bending of light because its speed changes in a different medium. It occurs at the boundary between two transparent media. The frequency of light stays the same during refraction.
Which statement represents Snell’s law for refraction from medium 1 to medium 2?
Correct Answer: B. n1 sin i = n2 sin r
Snell’s law is n1 sin i = n2 sin r for a fixed pair of media. It links angles with refractive indices. It is valid for a given wavelength and uniform media.
How is refractive index n related to speed of light in a medium?
Correct Answer: C. n = c/v
Refractive index is defined as n = c/v. Here c is speed of light in vacuum and v is speed in the medium. Larger n means smaller speed in that medium.
A ray goes from air into glass. How does it bend?
Correct Answer: B. Towards the normal
When light enters a denser medium like glass, its speed decreases. The ray bends towards the normal in this case. For the reverse path, it bends away from the normal.
Which quantity remains unchanged when light refracts from one medium to another?
Correct Answer: A. Frequency
Frequency of light remains the same during refraction. Speed and wavelength change when the medium changes. This is because frequency is set by the source.
When light enters a denser medium, what happens to its wavelength?
Correct Answer: A. It decreases
In a denser medium, speed of light decreases. Since frequency stays constant, wavelength must decrease. Wavelength changes as λ = v/f.
Which relation is correct for absolute refractive index n?
Correct Answer: B. n = c/v
Absolute refractive index is n = c/v. It compares light speed in vacuum to speed in the medium. It has no unit because it is a ratio.
For an object in water viewed from air near normal direction, the apparent depth is?
Correct Answer: C. less than real depth
Apparent depth is less than real depth when seen from a rarer medium. This happens due to bending of rays away from the normal on emerging. That is why the bottom looks raised.
Critical angle is defined for light going from?
Correct Answer: D. denser medium to rarer medium
Critical angle is defined only when light goes from denser to rarer medium. It is the angle of incidence for which the refracted ray makes 90 degrees. Beyond it, total internal reflection occurs.
Total internal reflection occurs when light travels from denser to rarer medium and?
Correct Answer: B. angle of incidence is greater than critical angle
Total internal reflection needs denser to rarer travel with i greater than critical angle. Then no refracted ray emerges into the rarer medium. The entire light reflects back inside the denser medium.