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Physics - Lizzie > Waves > Flashcards

Flashcards in Waves Deck (24):
1

Amplitude definition

The maximum disturbance from its undisturbed position.

2

Wavelength definition

The distance between a point on one wave and the same point on the next wave.

3

Time period definition

The time for one cycle of a wave to occur.

4

What is the difference between longitudinal and transverse waves?

• Transverse - the direction of the vibration is perpendicular to the direction of the wave.
• Longitudinal - the direction of the vibration is parallel to the direction of the wave.

5

Diffraction

• Diffraction happens when a wave passes an edge, passes through a narrow gap or goes past an object.
• Diffraction doesn't change any of the properties of a wave.
• The only thing that changes is the direction in which the wave is travelling.
• The diffraction effect is greatest when the width of the gap is about the same size as the wavelength of the wave.

6

What is the wave equation?

v = f x λ
speed = frequency x wavelength

7

Frequency deffinition

• The number of waves produced by a source each second.
• The number of waves that pass a certain point each second.

8

What is the electromagnetic spectrum?

• A continuous spectrum of waves.
• All the waves: transfer energy; are transverse; travel at the speed of light in a vacuum; can be reflected, refracted and diffracted.

9

What is the order of the electromagnetic spectrum in increasing frequency?

• Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.

10

What is the order of the electromagnetic frequency increasing in wavelength?

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

11

What is the order of the electromagnetic spectrum in increasing energy?

• Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.

12

What is frequency measured in?

Hz

12

What are the uses and dangers of microwaves?

• Used for cooking (water molecules in food absorb microwaves and vibrate very quickly - heat is produced and conducted/connected to other parts).
• Used for mobile phone and satellite communications.
• Can heat human body tissue internally if there is not a shield to prevent microwaves from reaching the user.

13

What are the uses and dangers of infrared?

• Infrared is heat radiation, so infrared cameras can detect humans in collapsing buildings and finding criminals in darkness.
• Used in electrical heaters to keep people warm.
• Used in grills to cook food.
• If there is an over-exposure to infrared, it can cause skin burns.

14

What are the uses and dangers of visible light?

• Used for seeing things - cameras require it to take pictures.
• Too much can cause permanent damage to the retina (e.g. looking at the sun).

15

What are the uses and dangers of ultraviolet?

• UV rays are used in fluorescent lights to emit visible light (fluorescent lights are more energy efficient than filament light bulbs).
• Too much UV can cause skin cancer, skin blistering/burns and blindness.

16

What are the uses and dangers of x-rays?

• X-ray radiation is directed through humans to find broken bones, as x-rays can pass through flesh but not bone.
• Exposure can cause mutations leading to cancer.

17

What are the uses and dangers of gamma rays?

• Gamma rays can kill all the microbes on medical instruments, sterilising them (better than boiling instruments, as some might be plastic and could be damaged by the hot temperatures).
• Can sterilise food, keeping it fresh for longer.
• Because they have high energy and frequency, gamma rays can penetrate very far into the body and cause cell mutation/destruction, which can subsequently cause tissue damage or cancer.

18

What is the difference between analogue and digital signals?

• Analogue signals can take any value within a certain range. The amp,it use and frequency of an analogue wave can vary continuously.
• Digital signals can only take two values (on/off or 1/0).

19

What are the advantages of digital signals?

• Regeneration of digital signals, on the other hand, creates a clean and accurate copy of the original signal, because it is easy to tell what the original signal was.
• The signal therefore becomes much sharper as the noise is not amplified.
• Digital signals can carry more information.

20

What are the uses and dangers of radio waves?

• Used mainly for communication - long-, medium- and shirt-wave radio; TV.
• Possibly causes of cancer, leukaemia and other disorders.

21

What can ultrasound be used for?

• Cleaning surgical instruments.
• Treating muscle strains.
• Treating cataracts.
• Breaking up kidney stones.
• Dentistry.
• Body scans.

22

How does sound change when it has a smaller amplitude and frequency?

• Becomes quieter.
• Pitch decreases/more bass.

23

How do x-rays show an image of a bone?

The x-rays emitted from a scanner are absorbed by the bone and cannot pass through it.