Ch11: Waves 1

Question 1

What are the features of a progressive wave?

Answer 1

An oscillation that travels through matter, or a vacuum. And transfers energy but not matter.

Question 2

What is a transverse wave?

Answer 2

A wave in which the oscillations are perpendicular to the direction of energy transfer.

Question 3

What is a longitudinal wave?

Answer 3

A wave in which the oscillations are parallel to the direction of energy transfer.

Question 4

What are some examples of a transverse wave?

Answer 4

Water waves, electromagnetic waves, waves on a stretched spring, s waves from earthquakes.

Question 5

What are some examples of a longitudinal wave?

Answer 5

Sound waves, P waves in an earthquake

Question 6

What is displacement in the case of waves?

Answer 6

Distance from equilibrium point, either positive or negative.

Question 7

What is amplitude of a wave?

Answer 7

Maximum displacement from equilibrium point

Question 8

What is wavelength of a wave and what is its symbol?

Answer 8

λ. The minimum distance between two in phase points of adjacent waves.

Question 9

What is the period of oscillation of a wave?

Answer 9

Time taken for a wave to move one wavelength past a given point.

Question 10

What is the frequency of a wave?

Answer 10

The number of wavelengths passing a given point per unit time.

Question 11

If a wave has frequency 7 Hz, how many complete oscillations occur a second?

Answer 11

7

Question 12

How do you find frequency from a period of a wave?

Answer 12

f=1/T T=period

Question 13

What is phase difference measured in?

Answer 13

Degrees or radians

Question 14

What is antiphase?

Answer 14

When two waves are at a phase difference of 180° or π radians.

Question 15

What is the angle between an incident ray and the normal?

Answer 15

Angle of incidence

Question 16

What is the incident ray?

Answer 16

The line of a ray entering a material.

Question 17

What is the angle of reflection?

Answer 17

The angle between the normal and the reflected ray.

Question 18

What happens to wavelength and frequency when a wave is reflected?

Answer 18

They don’t change

Question 19

When a wave slows down which way does it refract?

Answer 19

Toward the normal

Question 20

When a wave speeds up which way does it refract?

Answer 20

Away from the normal

Question 21

What is polarisation of a wave?

Answer 21

When a wave is made to only oscillate in one plane.

Question 22

How is intensity of a wave defined?

Answer 22

Power per unit area

Question 23

What is the equation for intensity? Define the terms.

Answer 23

I=P/A
I: intensity
P: power
A: area

Question 24

What is the relationship between intensity and distance from surface?

Answer 24

Intensity is inversely proportional to r^2. So when distance doubles, intensity reduces by a factor of four.

Question 25

If distance from the sun increased by 4, what would happen to intensity?

Answer 25

Decrease by a factor of 16.

Question 26

What is the relationship between intensity and amplitude?

Answer 26

Intensity is directly proportional to amplitude squared.

Question 27

What are the four properties of a wave?

Answer 27

Transfer energy Can be refracted Can be reflected Can be diffracted

Question 28

What is one property of a transverse wave, that longitudinal waves do not have?

Answer 28

They can be polarised.

Question 29

What is the equation for wave speed?

Answer 29

v=λf

Question 30

How can the v=fλ equation be modified for EM waves?

Answer 30

c=fλ (Because all EM waves travel very close to their speed in a vacuum, which is the same for all EM Waves including light.)

Question 31

How is refractive index of a material calculated and what is its symbol?

Answer 31

n=c/v n: refractive index c: speed of light in a vacuum v: speed of light in said material

Question 32

If the refractive index is larger, does it refract toward the normal or away?

Answer 32

Toward the normal - as it is going slower.

Question 33

What is the equation for the angle between the incident ray and the normal?

Answer 33

nsinθ=k n= refractive index k= constant

Question 34

How can the refractive index equation be used be used for light travelling from one medium to another?

Answer 34

nsinθ(one material)=nsinθ(second material)

Question 35

What are the two conditions for total internal reflection?

Answer 35

- The ray must be moving from a higher refractive index material into a lower refractive index material. - The angle it meets the boundary at must be larger than the critical angle.

Question 36

How is critical angle calculated?

Answer 36

sinC=1/n

Question 37

What is the relationship between refractive index and critical angle?

Answer 37

Greater the refractive index, n, the lower the critical angle, C.