Waves

Question 1

What do all waves transfer?

Answer 1

Energy without transferring matter.

Question 2

What are longitudinal waves?

Answer 2

Waves in which the direction of oscillations is parallel to the direction of energy transfer.

Question 3

What are compressions and rarefactions?

Answer 3

Compressions are when particles bunch up, and rarefactions are when they are spread out.

Question 4

What are transverse waves?

Answer 4

Waves in which the direction of oscillations is perpendicular to the direction of energy transfer.

Question 5

What is a waveform?

Answer 5

A representation of any wave, including longitudinal waves.

Question 6

What is displacement in wave terms?

Answer 6

How far the particles have oscillated from their original position.

Question 7

What is amplitude?

Answer 7

The peak of a wave, or the maximum displacement from equilibrium.

Question 8

What is wavelength?

Answer 8

The distance of one complete wave, represented by the symbol lambda (λ) and measured in meters.

Question 9

What is the time period of a wave?

Answer 9

The time it takes for one complete wave to pass.

Question 10

What is frequency?

Answer 10

How many waves pass a point every second, measured in hertz (Hz).

Question 11

What is the relationship between frequency and time period?

Answer 11

Frequency is equal to 1 over the time period (f = 1/t).

Question 12

What is the wave equation?

Answer 12

v = fλ, where v is wave speed, f is frequency, and λ is wavelength.

Question 13

What is the range of visible light wavelengths?

Answer 13

From around 400 to 750 nanometers (4 to 7.5 x 10^-7 meters).

Question 14

How does intensity relate to amplitude?

Answer 14

Intensity is proportional to the amplitude squared; if amplitude doubles, intensity quadruples.

Question 15

What happens to light waves when they move from one medium to another?

Answer 15

They change speed and wavelength, and this can result in a change in direction, called refraction.

Question 16

What is the refractive index?

Answer 16

A ratio equal to the speed of light in a vacuum divided by the speed of light in the medium.

Question 17

What is Snell’s law?

Answer 17

n1 sin(θ1) = n2 sin(θ2), where n is the refractive index and θ is the angle.

Question 18

What is the critical angle?

Answer 18

The angle of incidence that results in an angle of refraction of 90 degrees.

Question 19

What is total internal reflection?

Answer 19

When the angle of incidence exceeds the critical angle, resulting in all light being reflected back inside.

Question 20

How do optic fibers work?

Answer 20

They use total internal reflection, with a core surrounded by cladding that has a lower refractive index.

Question 21

What is modal dispersion?

Answer 21

The spreading of light as it travels down a fiber, resulting in pulse broadening.

Question 22

What is polarization?

Answer 22

The process where a polarizing filter only lets waves of certain orientations through.

Question 23

What happens when two progressive waves meet?

Answer 23

They undergo superpositioning, potentially forming a stationary wave.

Question 24

What are nodes and antinodes?

Answer 24

Nodes are points where the wave doesn’t move (destructive interference), and antinodes are points of maximum amplitude (constructive interference).

Question 25

What is the first harmonic?

Answer 25

The simplest stationary wave with one loop, one antinode, and nodes at both ends.

Question 26

How is the frequency of the first harmonic calculated?

Answer 26

Using the equation f = 1/2L √(T/μ), where T is tension and μ is mass per unit length.

Question 27

What is Young's double slit experiment?

Answer 27

An experiment demonstrating interference patterns of light through two slits.

Question 28

What is the path difference for dark fringes?

Answer 28

Half a wavelength (λ/2), resulting in destructive interference.

Question 29

What is Young's double slit equation?

Answer 29

w = λd/s, where w is fringe spacing, d is slit to screen distance, and s is slit separation.

Question 30

What is diffraction?

Answer 30

The spreading of waves as they pass through a slit or around obstacles.

Question 31

What happens when using a laser in experiments?

Answer 31

It provides coherent light, resulting in clearly defined fringes.

Question 32

How does wavelength affect diffraction?

Answer 32

Longer wavelengths, like red light, diffract more than shorter wavelengths, like blue light.

Question 33

Which color of light diffracts the most?

Answer 33

Red light diffracts the most due to having the longest wavelength.

Question 34

Which color of light diffracts the least?

Answer 34

Blue light diffracts the least due to having the shortest wavelength.

Question 35

What happens when Young's double slit is replaced with a grating?

Answer 35

You only get constructive interference at a few points far away from the central maximum.

Question 36

What is the central maximum referred to in terms of orders?

Answer 36

The central maximum is referred to as the zeroth order.

Question 37

What equation is used for large angles in diffraction?

Answer 37

The equation used is n lambda equals d sine theta.

Question 38

How is line spacing in a grating typically given?

Answer 38

It is often given in lines per millimetre, which needs to be converted to metres.

Question 39

How do you find the maximum visible order?

Answer 39

To find the maximum visible order, determine what order is made at 90 degrees.

Question 40

What is the value of sine 90 degrees?

Answer 40

Sine 90 equals 1.

Question 41

What is the formula to find the order at 90 degrees?

Answer 41

n equals d over lambda.

Question 42

If n equals 3.8, what does that imply about visible orders?

Answer 42

Only orders up to 3 are visible.

Question 43

How do you count visible orders?

Answer 43

Count the orders on both sides, including the zeroth order.

Question 44

What happens to the number of visible orders if the wavelength is halved?

Answer 44

If the wavelength is halved, n doubles.

Question 45

What does halving the wavelength do to the orders?

Answer 45

What was the first order becomes the second order, and a new first order is created.

Question 46

What is the relationship between n and d?

Answer 46

n is proportional to d.