Unit 4 Review Answer
Question 1
Wave
length
Crest
Amplitude
Trough
Question 2
• Wavelength – 2m
• Amplitude – 5 m
•
•
𝐶𝑦𝑐𝑙𝑒𝑠
F=
𝑠
1.5 𝑐𝑦𝑙𝑐𝑒𝑠
F=
0.3 𝑠
•
•
𝑠𝑒𝑐𝑜𝑛𝑑𝑠
1
P=
or
𝑐𝑦𝑐𝑙𝑒
𝐹
0.3 𝑠
P=
= 0.2
1.5 𝑐𝑦𝑙𝑐𝑒𝑠
𝑉
l = rearrange
𝐹
s/cycles
•
=5 cycles/s
• v = lF = (2)(5) = 10 m/s
Question 3
• Wavelength : C A B D
• Amplitude: D B A C
• Frequency: All the same
Question 4
• Sound travels through air at about 343 m/s.
Calculate the wavelength of the sound of
frequency 256 Hz.
• l=
• l=
𝑉
𝐹
343 𝑚/𝑠
256 𝐻𝑧
• l = 1.35 m
Question 5
• The ‘C’ above middle C on a piano has a
frequency of 512 Hz. Calculate its wavelength.
• l=
• l=
𝑉
𝐹
343 𝑚/𝑠
512 𝐻𝑧
• l = 0.67 m
Question 6
l = 3.7cm ÷ 100 = 0.037m
A= 1.7
cm
F=
𝐶𝑦𝑐𝑙𝑒𝑠
𝑠
3.5
0.7𝑠
F=
F= 5 Hz
P=
P=
𝑠
𝐶𝑦𝑐𝑙𝑒𝑠
0.7𝑠
3.5 𝑐𝑦𝑐𝑙𝑒𝑠
P = 0.2 cycles /s
𝑉
l = rearrange
𝐹
v = lF
v = (0.037)(5)
v = 0.185 m/s
Question 6b
l = 1.0 cm ÷ 100 =
0.01 m
A= 0.8 cm
F=
F=
𝐶𝑦𝑐𝑙𝑒𝑠
𝑠
12.5
=5
2.5𝑠
Hz
P=
P=
𝑠
𝐶𝑦𝑐𝑙𝑒𝑠
2.5𝑠
12.5𝑐𝑦𝑐𝑙𝑒𝑠
P = 0.2 cycles /s
𝑉
𝐹
l = rearrange
v = lF = (0.01)(5)
v = 0.05 m/s
Question 7
• Explain how sound travels. Does sound always
travel at the same speed? Explain your answer.
• Sound is transmitted by particles (atoms or
molecules) in a solid, liquid or gas colliding with
each other. Where there are no particles, no
sound can travel
• The speed of sound depends on the medium
through which it travels. The closer together the
particles, the faster sound travels.
Question 8
• A) No, the size of the image should be the same
as the object.
• B)Yes, same size, shape distance from the mirror
and observes the left-right side inversion rule
Question 9
Reflected light rays
Incident light rays
Object
Virtual image
Mirror
Virtual light rays
Question 10
R2 =
60 o
I1 =
30 o
R1 =
30 o
I2 =
60 o
Question 11