Chapter 6 - Combining Waves (up to page 108)

Question 1

What is superposition?

Answer 1

When two waves of the same type (e.g. two sound waves) overlap and interact. If the two waves meet in phase, they cause constructive superposition and the amplitude increases. If they meet in anti phase, then they destructively superimpose and the two waves cancel each other out

Question 2

What conditions are required for two waves to have a constant pattern of interference?

Answer 2

They must be of the same frequency, wavelength and have a constant phase relationship between each other (i.e. constantly anti phase or in phase)

Question 3

How does Young’s double slit experiment demonstrate the wave nature of light?

Answer 3

As the light formulates a stable interference pattern after going through the slits with crests and troughs, meaning that the light must be behaving as a wave, and not as a particle which would cause just two straight lines through the slits

Question 4

What order is the central fringe in Young’s double slit experiment?

Answer 4

n = 0

Question 5

What is the equation linking distance to the screen, wavelength, and fringe spacing?

Answer 5

Fringe spacing (w) = wavelength (lambda) x distance to the screen (D) / spacing between the slits (s)

Question 6

How is a stationary wave formed?

Answer 6

From two progressive waves of the same frequency and amplitude travelling in opposite directions

Question 7

What is a node?

Answer 7

A point of 0 amplitude on a stationary wave

Question 8

What is an antinode?

Answer 8

A point of maximum amplitude on a stationary wave

Question 9

What is the equation for frequency of a harmonic?

Answer 9

Frequency (f) = wave speed (v) / wavelength (lambda)

Question 10

What is the equation to find the speed of a harmonic on a string?

Answer 10

Speed (v) = [root]{tension (T) / mass per unit length (mu)}

Question 11

What forms at a closed end of a tube through which a sound wave is passing?

Answer 11

A node, as the particles cannot vibrate through the closed end

Question 12

Why do a lot of microwaves have rotating turntables?

Answer 12

As often despite the ability of microwaves to deflect off metal surfaces and thus bounce around within the oven, stationary waves still develop within the microwave - resulting in some overlooked patches where there are antinodes and undercooked ones at the nodes, thus keeping the turntable rotating allows the food to be cooked more evenly