Radiation Pressure — Practice Quiz

Question 1

Sunlight of intensity 1400 W/m² falls on a perfectly black absorbing surface. The radiation pressure is:

Accepted Answer

4.67 × 10⁻⁶ Pa

Answer

9.33 × 10⁻⁶ Pa

Answer

1.4 × 10⁻⁶ Pa

Answer

1.4 × 10⁻³ Pa

Question 2

The same intensity falls on a perfect MIRROR instead of an absorber. The pressure becomes:

Accepted Answer

Double

Answer

Same

Answer

Half

Answer

Quadruple

Question 3

A 100 W lamp radiates isotropically. The radiation force on a flat absorber of area 1 m² placed 10 m away (normal incidence) is:

Accepted Answer

2.65 × 10⁻¹⁰ N

Answer

0.265 × 10⁻¹⁰ N

Answer

1.06 × 10⁻¹⁰ N

Answer

5.3 × 10⁻¹⁰ N

Question 4

A solar sail (perfect reflector, area 100 m²) is in space at 1 AU. Force on it (solar constant 1361 W/m²):

Accepted Answer

≈ 9.1 × 10⁻⁴ N

Answer

≈ 9.1 × 10⁻⁵ N

Answer

≈ 4.5 × 10⁻⁴ N

Answer

≈ 1.4 × 10⁻³ N

Question 5

Why do comet tails point AWAY from the Sun?

Accepted Answer

Solar wind and radiation pressure overcome gravity on small particles

Answer

Sun's gravity pushes them away

Answer

They are repelled by Earth's magnetism

Answer

Conservation of momentum in orbit