Physics > Year 9 term 3 > Flashcards

Year 9 term 3 Flashcards

(56 cards)

Study These Flashcards
1
Q

Define a wave

A

It transfers energy but not matter through vibrations.

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2
Q

Deifne amplitude

A

Maximum movement of a wave from the equilibrium

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3
Q

Define a time period

A

Time for one wave to produce

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4
Q

Formula for wave speed

A

v= fλ

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5
Q

Formula for frequency

A

f=1/T

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6
Q

Formula for time period

A

T=1/f

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7
Q

Formula for critical angle

A

sin c=1/n

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8
Q

Formila for refractive index

A

n=sin i/sin r

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9
Q

Critical angle of a prism

A

(about) 42 degrees

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10
Q

Angle of incidence in a prism

A

45 degrees

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11
Q

What does “sin r” stand for in the formula of refrective index

A

angle of refraction

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12
Q

define a light pipe

A

A pipe, even when it is curved it will provide a path to the light.

Example : optic fibres

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13
Q

Outline how a ripple tank works

A
  1. Electric motor vibrates on a piece of wood
  2. Wood vibrations make ripples in water
  3. Light above draws shadows of these waves onto the pannel below
  4. We can now measure frequency and time periods
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14
Q

Refractive index of water

A

1.3

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15
Q

Refractive index of air

A

1.5

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16
Q

How can sound waves be refracted?

A

Warm air—> cool air and vice versa

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17
Q

Why do people use optic fibres in preference to copper in telecommunications?

A

Less electricity used/wasted by them.

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18
Q

Outline a simple experiment to find the speed of sound

A
  1. Stand 50m away from your friend
  2. Your friend has 2 pieces of wood, she bangs them.
  3. start a timer immediately
  4. as soon as you hear the echo stop the timer
  5. use the formula s=d/t
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19
Q

Describe how a sonar calculates the distance of the bottom of the boat to the ocean floor

A
  1. Sonar emits sound
  2. Sound reaches sea floor
  3. sound reflects
  4. sound reaches boat
  5. Sonar divides time by 2, and with the knowledge of seed of these sound waves uses the formula s=d/t as d=st to find the distance.
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20
Q

What does an oscilloscope do?

A

Turn longitudinal waves into transverse waves so we can see them and measure the frequency and time periods of sounds.

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21
Q
A
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22
Q

What is the human hearing range?

A

20-20,000Hz

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23
Q

Ultra sound is….

Study These Flashcards
A

Above hearing range of humans

24
Q

Is ultra sound safe?

25
Define infra sound
Below human hearing range
26
A dog whistle is ultrasound/infrasound?
Ultrasound
27
What changes in refraction
The wavelength
28
Define refraction
The bending of light as it slows down/speeds up by passign through different mediums
29
In glass, the Angle of refraction is ---- the medium, when exiting glass, the angle of refraction turns ---- from the normal
1. Towards 2. Away
30
The ----- the frequency the higher the pitch.
Higher
31
3 places where prisms are used for total internal reflection?
- Binoculars - Bicycle blinkers - Periscopes
32
Sound is a ----- wave
longitudinal
33
Light is a ------ wave
Transverse
34
Defien wave front
Where overlapping waves can have a line pass through them as the share the same distance froms ource and vibrations
35
Formula of amplitude in a wave
Amplitude=distance of 2 particles/2
36
Defien a transverse wave
1. Oscillations travel 90 degrees/perpendicular to the direction of motion 2. Has KE 3. Energy moves left---> right
37
Define a longitudinal wave
1. Have compressions and refractions 2. moves left and right, not up and down 3. Transfer information 4. Direction of disturbance is the same as direction of motion.
38
Define a period
time for single wave to pass
39
Frequency is ---- --- to period
Inversley proportional
40
Define the doppler effect
- Apparent difference in frequency of light or sound waves as they move towards/away fromt he observer.
41
Outline what happens to the waves in the doppler effect
The waves will "spread out" more when leaving the observer and compress upon nearing the observer, in both cases a wavefront is not present.
42
Recall the EM spectrum in order from lowest to highest frequency
- Radio waves - Microwaves - Infrared waves - Visible light - UV rays - x-rays - Gamma rays
43
Features every ray in the EM shares
- Can all travel through a vaccum - In vaccum at 3x10^8 m/s - Transfer energy from source to observer - Can be reflected or refracted - They are all transverse - can all carry energy
44
Uses of radio waves
- Broadcasting - Communicators
45
Uses of microwaves
- Mobile phones(messages) - Cooking - satelites ## Footnote The waves heat up the water molecules in the food, hence cooking the whole food and not just some of it.
46
Uses of IR waves
- Heaters - Night vision equiptment
47
Uses of visible light
- Optical fibres - Photgraphy
48
Uses of UV rays
- Florescent lamps - Black light for security - Tanning/tanning beds - Security notes/criminal sweat traces.
49
Uses of x-rays
- Fractures - Treat tumors - Observing organs
50
Uses of Gamma rays
- Sterilizing food/equiptment - Treating cancer/killing cancerous cells
51
Formula of wavelength
Wavenlength=1/f
52
Dangers of Microwaves
- Internal heating - heating body tissues
53
Dangers of IR rays
Skin burns
54
Dangers of Gamma radiation
- Cancer - Mutation of cells
55
Dangers of UV rays
- Damage to surface cells - Blindness
56
Dangers of x-rays
- mutations - cancer
Physics
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