3. Waves Flashcards

(50 cards)

1
Q

What do waves do

A

Waves transfer energy and information without transferring matter

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2
Q

Define frequency and give its units

A

● The number of waves passing through a point per second.

● Hz (hertz)

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3
Q

Define wavelength

A

The distance between two adjacent

peaks on a wave

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4
Q

Define amplitude

A

● The maximum displacement of the
wave from its equilibrium position.
● The distance between the centre of
the wave and a peak

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5
Q

What is meant by the period of the

wave?

A

The length of time it takes for ONE FULL WAVE to pass through a point

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6
Q

How can you calculate the wave speed?

A

● Wave speed (measured in metres per second) is equal to the product of the wavelength and the frequency of the wave.
● Wave velocity= f ×λ

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7
Q

State an equation linking frequency and

period of a wave

A

frequency (Hz) = 1/ time period

f = 1/T

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8
Q

What is a longitudinal wave? Give some

examples

A

● Vibrations are parallel to the direction of
energy transfer(wave)
● Examples include sound waves and
earthquakes (seismic waves)

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9
Q

What is a transverse wave? Give some

examples.

A
● A wave with oscillations that are
perpendicular ( 90 degrees) to the
direction of energy transfer.
● Examples include electromagnetic
waves
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10
Q

Explain what is meant by “the Doppler effect”

A

Apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer. When a wave source is moving towards the observer, observed frequency increases and observed wavelength decreases; when a wave source is moving away from the observer, observed frequency decreases and observed wavelength increases since v= f ×λ and speed in constant

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11
Q

At what speed does an electromagnetic

wave travel in a vacuum?

A

3 x10^8 m/s

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12
Q

What types of waves are electromagnetic waves?

A

Transverse

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13
Q

What do electromagnetic waves

transfer?

A

Energy and Information

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14
Q

What are the four common properties of all electromagnetic waves?

A

· They are all transverse waves
· They all transfer energy or information
· They all travel at the speed of light in vacuum
· They all can be reflected, refracted or diffracted

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15
Q

Which part of the electromagnetic spectrum has the longest wavelength?

A

Radio waves

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16
Q

Order the electromagnetic spectrum from
the highest frequency to the lowest
frequency

A

Gamma rays, x-rays, ultraviolet, visible
light, infrared, microwaves and radio
waves

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17
Q

What are the colours of the visible light spectrum?

A

Red, Orange, Yellow, Green, Blue, Violet

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18
Q

a. Which colour has the highest frequency?
b. Which colour has the lowest frequency?
c. Which colour has the lowest wavelength?
d. Which colour has the highest wavelength?

A

a. Violet
b. red
c. violet
d. red

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19
Q

What are the uses of radio waves?

A

● For communication through radio

● Used for satellite transmissions

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20
Q

What are microwaves used for?

A

● Cooking in microwaves ovens
● Communications
● Satellites

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21
Q

Which part of the electromagnetic
spectrum is used in cooking, thermal
imaging and television remote controls?

22
Q

Give examples of uses for visible light?

A

● Allows us to see (used for vision)
● Photography
● Optical Fibres
(endoscope,communication)

23
Q

What part of the electromagnetic
spectrum is used to for security marking
and in fluorescent lamps?

24
Q

What are some uses of x-rays?

A

● Scanners at airports

● Medical x-ray machines

25
What are the uses and disadvantages of | gamma rays?
● Used to sterilise food and medical equipment ● Used in cancer diagnosis ● Can cause mutations or damage to body cells. This could lead to death.
26
What are the disadvantages of | microwaves?
They can cause heating of internal | tissues in the body
27
Which part of the electromagnetic spectrum is used in TV remotes and can also cause skin burns?
- Infrared
28
Does the danger that is associated with electromagnetic waves increase with frequency or with wavelength?
With frequency
29
What are the dangers of excessive | exposure to ultraviolet?
You could damage your eyes and the cells on the surface of your skin. This could lead to skin cancer or eye conditions
30
What is the normal (in terms of reflection | and refraction)?
A vertical imaginary line which is | perpendicular to the boundary
31
What happens when light is reflected off | a boundary?
It is reflected (bounces) off a smooth flat surface so that the angle of incidence (the angle it comes in at) is the same as the angle of reflection (the angle it leaves at).
32
What happens when light is refracted | while passing through 2 different media?
● The light changes speed and direction in the new medium ● If the new medium is more dense, the light will travel slower and bend towards the normal ● If the new medium is less dense, the light will travel faster and bend away from the normal
33
State an equation linking angle of incidence, angle of | refraction and refractive index
n = sin(i)/sin(r) ``` n= refractive index i= angle of incidence r= angle of refraction ```
34
What is the critical angle?
The angle of incidence which causes the angle of reflection to be 90 degrees so that that the light refracts onto the boundary.
35
State an equation linking critical angle | and refractive index
n = 1/sin(c)
36
What is total internal reflection?
When light is trying to pass from a less dense medium to a denser medium, it can be reflected back to the less dense medium if the angle of incidence is larger than the critical angle between two media. This reflection is called Total Internal Reflection
37
State two uses of total internal reflection
- Endoscopes - Periscopes - Optical Fibres - Cat Eye Reflectors - Shining of Diamonds
38
If light hits a boundary at 90 degrees to | the surface, will the light refract?
No, it will not
39
Is light an example of a transverse or longitudinal wave?
Transverse
40
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-
41
What is the law of reflection
Angle of incidence = angle of reflection
42
What is the law of refraction
All waves can be refracted, which is when the speed of a wave changes when it enters a new medium
43
What happens if a wave enters a denser medium
Its speed decreases and it bends towards the normal
44
What happens if a wave enters a less dense medium
Its speed increases and it bends away from the normal
45
What happens to the velocity of a wave when refraction occurs
In all cases, the frequency stays the same but the wavelength changes. As a result, the velocity must change.
46
Sound waves are ...... waves and can be reflected and refracted
Longitudinal
47
The range of audible frequencies for a healthy human ear is ........
20 Hz to 20,000 Hz.
48
How can you measure the speed of sound in the air
- To measure the speed of sound in air, you can make a noise at a known, large distance from a solid wall and record the time for the echo (reflected sound) to be heard, then use speed = distance/time, where distance is 2 x length - taking into account the fact that the sound had to go there and back - An oscilloscope connected to a microphone can be used to display a sound wave and find its frequency and amplitude.
49
The greater the amplitude of a sound wave, the ...... it is.
Louder
50
The greater the frequency of a sound wave, the .....
Higher its pitch