Unit Review Questions

Question 1

List the electromagnetic waves in order from lowest energy to highest energy: green light, microwaves, X-rays, ultraviolet light, infrared light, red light, and radio waves.

Answer 1

radio waves, microwaves, infrared light, red light, green light, ultraviolet, x-rays

Question 2

Order the colours of the rainbow from shortest wavelength to longest wavelength.

Answer 2

Violet, indigo, blue, green, yellow, orange, red

Question 3

True or False. In order to see an object, light must reflect from that object into your eyes.

Answer 3

True

Question 4

List the seven colours that Newton identified in the visible spectrum of white light.

Answer 4

red, orange, yellow, green, blue, indigo, violet

Question 5

What is the relationship between frequency and wavelength of a wave?

Answer 5

As the frequency increases, the wavelength decreases.

As the frequency decreases, the wavelength increases.

Question 6

What colours are absorbed in a green object? What colours are reflected from a green object?

Answer 6

Red and Blue light is absorbed. Green light is reflected.

Question 7

What colours are absorbed in a black object? What colours are reflected from a black object?

Answer 7

White light is absorbed. No colour reflected.

Question 8

What colours are absorbed in a white object? What colours are reflected from a white object?

Answer 8

White light is absorbed. All colours reflected.

Question 9

What is the main difference between phosphorescence and fluorescence?

Answer 9

Fluorescent materials absorb light of one wavelength and emits light of another wavelength.

Phosphorescent materials are charged by exposure to UV light. These materials release the energy slowly over time.

Question 10

What would the angle of incidence be for an angle of reflection of 47 degrees?

       (REFLECTION OF PLANE MIRRORS)

Answer 10

angle of incidence = angle of reflection

therefore the angle of incidence would be 47o to the normal

Question 11

What are the two rules of reflection for a plane mirror?

Answer 11

rule #1: angle of incidence = angle of reflection

rule #2: distance of the object in front of the mirror = distance of the image behind the mirror

Question 12

Where must an object be located in order for a concave mirror to form:

a) A real image
b) A virtual image

Answer 12

a) Real Image: Anywhere outside of the focal point.

b) Virtual Image: Between the focal point and the mirror.

Question 13

Why will a convex mirror NEVER form a real image?

Answer 13

Rays will never cross in front of the mirror

rather the rays will appear to spread out from a point behind the mirror

Therefore, creating a virtual focal point or virtual image

Question 14

What are the three principal rays of a curved mirror?

Answer 14

Rays that travel parallel to the principal axis will always reflect through the focal point.
Rays that travel through the focal point will always reflect parallel to the principal axis.
Rays that pass through the center of curvature will always reflect back on itself.

Question 15

What type of mirror produces diverging rays?

Answer 15

Diverge means to spread out.

A convex mirror causes light rays to spread out (diverge)

Question 16

What type of mirror can produce converging and diverging rays?

Answer 16

The word converge means to meet at a point.
The word diverge means to spread out from a point.
A concave mirror can produce both converging and diverging rays depending on where the object is placed.

1. when object between focal point and mirror = diverging rays
2. when object outside of focal point = converging rays

Question 17

Light bends toward the normal when going from material A into material B. Compare the speed of light in the two materials.

Answer 17

speed of light in material A = faster

speed of light in material B = slower

Question 18

What TWO conditions must be satisfied for total internal reflection to occur?

Answer 18

Light must be travelling from a slow medium to a fast medium.
Angle of incidence must be greater than the critical angle.

Question 19

A certain substance has a critical angle of 24.5º. What minimum angle of incidence, to the nearest tenth of a degree, will result in total INTERNAL reflection?

Answer 19

The critical angle of this material is 24.5 degrees, therefore light will reflect internally for any angle of incidence greater than this angle. Therefore, according to the given condition, total internal refraction of light will take place at angle 24.6 degrees.

Question 20

A beam of light is travelling from air to glass. Would refraction still occur if light travelled at the same speed in both air AND glass? EXPLAIN.

Answer 20

No. Because the speed of light is the same in both material.
Refraction occurs when the speed of light changes due to the different optical density of the materials.

Question 21

What are the three rules of refraction for any lens?

Answer 21

When a light ray travels parallel to the principal axis, it will always refract through the primary focus.

When a light ray travels through the secondary focus, it will refract parallel to the principal axis.

When a light rays travels diagonally through the center of the lens, it will continue straight through without refracting.

Question 22

Light traveling through an optical fiber (n=1.44) reaches the end of the fiber and exits into air.
(a) If the angle of incidence on the end of the fiber is 30º, what is the angle of refraction outside the fiber?

Answer 22

(1.44) sin 30º = 1.00 sin θ2.
sin θ2 = (1.44/1.00) sin 30º = 1.44 (0.500) = 0.720
θ2 = sin-1 (0.720) = 46º.

Question 23

What is the shape of your lens when viewing distant objects? What is the shape of your lens when viewing nearby objects?

Answer 23

distant objects = lens flatter (ciliary muscles relax)

near objects = lens thicker(ciliary muscles contract)

Question 24

What type of lens should a person who is far sighted use? What type of lens should a person who is nearsighted use?

Answer 24

near sighted - concave lens (lengthen the focal point)

far sighted - convex lens (shorten the focal point)

Question 25

If a room is dark, what happens to the iris?

Answer 25

The iris dilates (becomes larger) maximize the amount of light entering the lens. The pupil (black hole at the center of eye) will appear larger

Question 26

If a room is really bright what happens to the iris?

Answer 26

The iris constricts (becomes smaller) to minimize the amount of light entering the lens. The pupil (black hole at the center of eye) will appear smaller.

Question 27

What does the iris do?

Answer 27

The iris regulates the amount of light that enters the lens of the eye.