Wave Properties Flashcards

1
Q

What type of waves are electromagnetic waves?

A

Transverse waves, they travel as vibrations through magnetic and electric fields, with vibrations perpendicular to the direction of energy transfer

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2
Q

What are wavefronts?

A

Surface containing points affected in the same way by a wave at a given time

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3
Q

What is the angle in which waves reflect at, from hard flat surfaces?

A
  • Straight waves directed at a certain angle to a hard flat surface, reflect off at the same angle.
  • Angle between the reflected wavefront and surface is the same as the angle between incident wavefront and the surface
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4
Q

What occurs when waves pass across a boundary in which wave speed changes?

A
  • When waves pass across a boundary at which the wave speed changes, the wavelength also changes
  • If wave fronts approach at an angle to the boundary they change direction as well as changing speed
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5
Q

What happens if waves approach a boundary at which the wave speed changes, at an angle?

A
  • If wave fronts approach at an angle to the boundary they change direction as well as changing speed
  • This effect is known as refraction
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6
Q

When does diffraction occur?

A

Diffraction occurs when waves spread out after passing through a gap or round an obstacle

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7
Q

How does gap size affect diffraction?

A
  • The narrower the gap the more the waves spread out

* The longer the wavelength, the more the waves spread out

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8
Q

Why are waves diffracted?

A
  • Each point on a wavefront is a secondary emitter of wavelets
  • Wavelets from the points along a wavefront travel only in the direction in which the wave is travelling
  • Not in the reverse direction
  • Combine to form a new wavefront spreading beyond the gap
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9
Q

What happens if the gap is bigger than the wavelength?

A

Diffraction is unnoticeable

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10
Q

When does noticeable diffraction occur?

A

When the gap is several wavelengths wide

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11
Q

When do you get the most diffraction?

A

When the gap is the same size as the wavelength

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12
Q

What happens if the gap is smaller than the wavelength

A

Waves are mostly reflected back

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13
Q

What is required to observe a clear diffraction pattern?

A

You need to use a monochromatic coherent light source

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14
Q

What is intensity?

A

Power per unit area

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15
Q

Why are satellite TV dishes pointed south?

A

• Because satellites orbit the earth directly above the equator, the larger the dish the stronger the signal it can receive.

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16
Q

Why does dish size affect how strong of a signal it can receive?

A
  • Bigger the dish the stronger signal it can receive
  • More radio waves are reflected by the dish onto the aerial, but a bigger dish reflects the radio waves to a smaller focus, because it diffracts waves less
  • Bigger dish needs to be aligned more carefully than a smaller dish otherwise it will not focus the radio waves onto the aerial