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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

What are transverse waves?

A

In transverse waves the oscillations are PERPENDICULAR (right angles) to the direction of energy transfer.

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2
Q

Give an example of a transverse wave.

A

Any 1 from:

  • vibrations in string,
  • ripples on water surface
  • electromagnetic waves
  • light
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3
Q

What are longitudinal waves?

A

In longitudinal waves the oscillations are PARALLEL to the direction of energy transfer.

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4
Q

What is key about waves in general?

A

For both ripples on a water surface and sound waves in air, it is the WAVE that travels NOT the WATER or the AIR molecules.

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5
Q

What is meant by an electromagnetic wave?

A
  1. They are TRANSVERSE WAVES.
  2. They transfer ENERGY from the SOURCE of the waves to an ABSORBER.
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6
Q

What does a microwave oven do?

A

Microwaves transfer ENERGY from the SOURCE (the oven) to the ABSORBER (food).

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7
Q

What happens when you pass white light into a prism?

A

It splits into a SPECTRUM: red, orange, yellow, green, blue, indigo and violet

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8
Q

What happens to the frequency from radio waves to gamma rays?

A

It increases.

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9
Q

What happens to the wavelength from radio waves to gamma rays?

A

It decreases.

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10
Q

Do electromagnetic waves need a medium to travel in?

A

No, meaning electromagnetic waves can travel through a VACUUM (eg in space).

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11
Q

What same speed do electromagnetic waves travel through a vacuum at?

A

……………………………………..8

300 000 000 m/s (3x10 m/s)

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12
Q

What happens when light passes from the air into glass?

A

The VELOCITY of light DECREASES, causing the DIRECTION of the waves to change.

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13
Q

How can refraction be shown? [4]

A
  1. Draw on the NORMAL at right angles to the surface of the glass.
  2. When waves slow down they bend TOWARDS THE NORMAL.
  3. The light waves now pass THROUGH the glass block.
  4. When the waves pass from the GLASS back to the air, their VELOCITY INCREASES (BEND AWAY from the NORMAL).
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14
Q

What happens when the ray of light enters the block along the normal?

A

It does not change dircetion

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15
Q

What is meant by a wavefront?

A

It is an imaginary LINE that connects all the SAME POINTS in a set of waves. (Make it easier to visualise lots of waves moving together).

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16
Q

What is a Leslie’s cube?

A
  • Used to see how much INFRARED IS EMITTED from different surfaces.
  • It has 4 DIFFERENT SURFACES (shiny metallic, white, shiny black and a matt black).
17
Q

How can we measure how much infrared is emitted?

A
  • Fill the Leslie’s cube with HOT WATER.
  • Then point an INFRARED DETECTOR at each of the four surfaces and record amount of infrared emitted.
18
Q

What can be used instead of an infrared detector?

A

A THERMOMETER with the bulb painted BLACK. However the RESOLUTION of the thermometer is LESS than the infrared detector.

19
Q

How can we measure how much infrared is absorbed?

A
  • We have an INFRARED HEATER and on either side we have TWO METAL PLATES.
  • One plate has been painted with SHINY METALLIC paint.
  • The other with MATT BLACK paint.
  • On the other side of the plates, we have used VASELINE to attach a DRAWING PIN.
  • We now switch on the HEATER and start TIMING.
  • We record the time it takes for the VASELINE TO MELT and the drawing pins to FALL OFF (matt black FIRST).
20
Q

What happens when electromagnetic waves are generated or absorbed?

A

CHANGES take place in ATOMS or in the NUCLEI of atoms.

21
Q

What happens when we heat lithium for example?

A
  • We cause electrons to MOVE from one energy level to a HIGHER ONE. - When this electron RETURNS to its original energy level, it generates an EM WAVE (light).
22
Q

Give on thing ultraviolet waves can do to the human body?

A

Any 1 from:

increase the risk of SKIN CANCER

cause the skin to AGE PREMATURELY

23
Q

What is similar about X rays and gamma rays?

A

They are IONISING RADIATION (KNOCK ELECTRONS OFF atoms when they are absorbed).

24
Q

What is the dose of radiation measured in?

A

sieverts (Sv)

25
Q

What is the range of wavelengths for waves in the electromagnetic spectrum?

A

…………………………..-15…….4

Approximately 10 to 10 meters

26
Q

Label the following on a wave: amplitude, wavelength, trough and crest

A

Physics (10 decks)

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