Refraction — Set 7

Correct Answer: B. total internal reflection inside the diamond

Diamond has a high refractive index, giving a small critical angle. Light entering it often undergoes total internal reflection many times. This makes more light emerge back and appears as sparkle.

Correct Answer: A. 24 degrees

Use sin c = 1/n for diamond to air. With n = 2.42, sin c ≈ 0.413. This gives c about 24 degrees.

Correct Answer: D. a little before actual sunrise

Atmospheric refraction bends sunlight as it passes through layers of air. This makes the Sun appear higher than its true position. So we can see the Sun a little before actual sunrise.

Correct Answer: D. slightly higher than their true position

Light from stars bends as it enters denser layers of the atmosphere. This bending makes the apparent position shift upward. So stars appear slightly higher than their true position.

Correct Answer: C. 41 degrees

Use sin r = sin i / n for air to water. With i = 60 degrees, sin r = 0.866/1.33 ≈ 0.651. This gives r about 41 degrees.

Correct Answer: C. n = c/v

Absolute refractive index is defined as n = c/v. It compares the maximum speed of light in vacuum to its speed in the medium. It is dimensionless and depends on wavelength.

Correct Answer: B. 49 degrees

Use Snell’s law for air to glass: sin i = n sin r. With n = 1.5 and r = 30 degrees, sin i = 1.5×0.5 = 0.75. This gives i about 49 degrees.

Correct Answer: A. air

Air has refractive index very close to 1 for visible light. Water and glass have higher refractive indices than air. Diamond has a much higher refractive index than all of these.

Correct Answer: C. 0 degrees

Along the normal, the angle of incidence is zero degrees. Snell’s law then gives the angle of refraction also zero degrees. The ray continues straight without bending.

Correct Answer: B. 1.5

Use n = c/v for refractive index. Substituting c = 3.0×10^8 and v = 2.0×10^8 gives n = 1.5. A larger n means light travels slower in that medium.