Unit 2

Question 1

Principle of reversibility

Answer 1

light can travel the same path forward as it can reverse. Fermat’s principle

Question 2

Rectilinear propagation

Answer 2

Light from a point A to point B propagates in straight line if there is nothing between or if the medium is homogenous. Sun rays CAN be bent in some cases

Question 3

penumbra

Answer 3

partial shadow

Question 4

temperature and refractive index

Answer 4

temperature can change refractive index

Question 5

What would not be a factor for a solar eclipse to happen?

Answer 5

Sun being brighter than the moon

Question 6

When do we expect mars to transit across the sun?

Answer 6

never. Only inner planets will transit between the earth and sun

Question 7

transparency

Answer 7

relative. depends on what kind of radiation you use

Question 8

wavefront

Answer 8

spaced one wavelength apart vertically. ALWAYS perpendicular to rays. a surface of constant phase, help with wave nature analysis such as diffraction.

Question 9

Rays

Answer 9

Imaginary, straight, always perpendicular to wavefton, correspond to direction of propagation

Question 10

Huygen’s principle

Answer 10

Light propagates from point to point. Wavelets, can predict path of light