What does this mean?(1)
The waves have the same frequency and are "in phase".
2.
Name two points that are
a) in phase and(1) C and F
b) completely out of phase.(1) E and F (or C and E)
3. What happens to the frequency of sound waves during interference?(1)
No change - frequency is determined by the source.
4. Water waves have a wavelength of 4 m and a speed of 3 m/s.
a) Calculate the frequency of the waves.(2)
v = f λ
3 = f x 4
f = 3/4 = 0.75 Hz
b) Calculate the time it takes one wave to pass a point.(2)
T = 1 / f = 1 / 0.75 = 1.33 s
5. Which part of a water wave will increase in size if the wave has more energy?(1)
The amplitude increases.
6.What is constructive interference?(1)
Two crests or two troughs combine to produce a wave with a greater amplitude. pd = n λ
7. For destructive interference
a) Do the waves meet in phase or out of phase?(1)
Out of phase
b) State the formula for path difference when we have destructive interference.(1)
pd = (n + ½)λ
8. Name the wave property that is the test of a wave.(1)
Interference
9. Name the three other characteristic behaviours of waves.(3)
Reflection, refraction and diffraction.
10. Which colour of light in the visible spectrum has the longest wavelength?(1)
Red
11. Which wavelength will diffract the most, long or short?(1)
long waves diffract more.
12.
From S1 to point X is 68 cm.
From S2 to point X is 62 cm.
a) Calculate the wavelength of the microwaves.(2)
n = 2 constructive.
pd = n λ
6 = 2 λ
λ = 6 / 2 = 3 cm
b) Calculate their frequency.(2)
v = f λ
3x108 = f x 0.03
f = 1x1010 Hz
13. State the approximate wavelengths for
a) red light(1)700 nm to 600 nm
b) green light(1)600 nm to 500 nm
c) blue light.(1)500 nm to 400 nm
14.
a) Calculate the wavelength of these light waves.(3)
d = 1x10-3 / 500 = 2x10-6 m
n λ = d sinθ
2 x λ = 2x10-6 sin36°
λ = 588 nm
b) What colour is this light?(1)Green (or yellow.)
15.
The interference fringes shown are produced by red, green and blue light.
Which one is most likely to be the blue light?(1)
Fringe C: blue light has small wavelengths so the fringes are closer.
16. When projecting white light through a grating
I) a white central maximum is observed
II) several spectra are produced
III) blue fringes are nearest to the centre.
How do these three observations compare with white light dispersed into a spectrum by a prism?(3)
I) No white central maximum is produced.
II) Only one spectrum is visible.
III) Red light is nearest to the original direction of the ray as red light is refracted the least.
17.
Which of the following changes will increase the fringe spacing on the screen?(2)
a) Move the screen to the right, further away from the grating.
b) Use blue light instead of green.
c) Move the source of the green light to the left, further away from the grating.
d) Use a grating with more lines per meter.
A and D.
18.
A beam of white light is directed through a grating with 600 lines/mm.
Calculate the angle between the red and violet ends of the spectrum for the first order maximum.(4)
Find the angle for blue/violet light.
n λ = d sinθ
1 x 400x10-9 = (1x10-3/600) sinθ
sinθ = 0.240
θ = 13.9°
Now the angle for red light.
n λ = d sinθ
1 x 700x10-9 = (1x10-3/600) sinθ
sinθ = 0.419
θ = 24.8°
Angle difference θ = 24.8 - 13.9
θ = 10.9°
Total marks = 39