Light

Question 1

What is the Law of Reflection?

Answer 1

i = r

angle of incidence = angle of reflection

Question 2

(Practical) How do you investigate reflection?

Answer 2

1. Use a vertically upright plane mirror.
2. Mark out a dotted line on the paper for a normal
3. Label the intersection of the normal and mirror as ‘x’
4. Switch the ray box on, direct it to point ‘x’
5. measure i and r
6. repeat!

Question 3

What are the properties of a mirror image?

Answer 3

1. sizes are the same
2. distance from plane mirror is the same as distance from the virtual image
3. Image is laterally inverted.

Question 4

Refraction of Light

Answer 4

Refraction is when light experiences a change of speed at the boundary of two optical media.

Question 5

(Practical) Investigating Refraction:

Answer 5

1. Place a glass block on a sheet of paper
2. trace along it
3. Use a ray box to shine a light through the glass back at the normal (control)
4. Use another one to shine a light through the glass block at an angle
5. trace the incident ray and refracted ray
6. choose various angles.

Question 6

What is Snell’s Law?

Answer 6

sin i / sin r = constant

Question 7

What is the refractive index?

Answer 7

n = c / v

n = speed of light in a vacuum / speed of light in the medium

speed of light = 3.0 x 10⁸m/s

Question 8

What is total internal reflection?

Answer 8

Total internal reflection can only occur when an optically denser medium to a less dense medium.

Question 9

What is a critical angle?

Answer 9

The critical angle is the angle of incidence for which the angle of refraction - to a less dense medium - is 90^o

If the angle of incidence is larger than the critical angle, total internal reflection occurs.

Question 10

What equation can help find the critical angle?

Answer 10

n = 1 / sin c

Question 11

How is total internal reflection applied?

Answer 11

1. Glass Prisms
2. Optical Fibres (light does not escape even if bent. higher carrying capacity, ;less signal degradation, cheaper)

Question 12

What determines the path of light through a lens?

Answer 12

Converging Lenses (Thicker at the Center): eye-shaped; half-eye shaped; beginning bracket

Diverging Lenses (Thinner at the center): Pillar-like; outer straight bracket; outer bracket

Question 13

Parts of Thin Converging Lenses

Answer 13

Principal Axis: horizontal line through the center

principle focus: where all the rays converge

focal length: distance between C and F

optical centre: midpoint of surfaces of the lens

focal plane: passes through focal point, perpendicular to the principal axis.