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MED 101- PHYSICS I > ELECTROMAGNETIC WAVES > Flashcards

ELECTROMAGNETIC WAVES Flashcards

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1
Q
  1. What is light an example of?
A
  • an electromagnetic wave (EM)
  • it is self propagating
  • it consists of oscillating electric and magnetic fields
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2
Q
  1. How can light be shown?
A
  • as a changing electric field that causes a change in the
    magnetic field
  • or vice versa
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3
Q
  1. What is a waving electric field?
A
  • it is a field that causes similarly waving magnetic fields
    to act
  • they act at right angles to the waving electric field

THESE OSCILLATING FIELDS:
- they have sinusoidal movement
- they travel through space at a fixed speed
- this speed is known as c
- this is the speed of light

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4
Q
  1. When is a self-supporting process possible?
A
  • when the electromagnetic wave propagates at a
    certain speed
  • this speed is 299 792 458 m/s in a vacuum
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5
Q
  1. What is the speed of light?
A
  • 299 792 458 m/s
  • it is of fundamental importance in physics
  • it is the same for all observers
  • this is regardless of direction or speed
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6
Q
  1. How do we calculate the speed of light in a vacuum?
A

c = f . λ

c = speed of light (m/s)
f = frequency (Hz)
λ = wave length (m)

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7
Q
  1. Electromagnetic waves have a large range of wavelengths.
    What are the wavelengths for Visible light?
A
  • it has a wavelength of between 380 nm and 750 nm
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8
Q
  1. What are different frequency ranges in the spectrum generated by?
A
  • they are generated by different physical processes
  • they interact differently with matter
  • they are given different labels
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9
Q
  1. What is Refraction?
A
  • this is when a ray of light is transmitted obliquely
  • it is transmitted through a boundary
  • this boundary is between two materials of unlike index
    of refraction
  • this causes the ray to bend

OBLIQUELY= indirectly, slant wise

NB:
- the wave is changed
- the frequency is constant
- the wave length is changed
- this is due to the different speeds of light
- this is due to the different objects that the light pass
through
- these objects have different densities

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10
Q
  1. How is the Absolute Index of Refraction calculated?
A
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11
Q
  1. How do we calculate the relative index of the refraction of material 1 with respect to material 2?
A
  • this is used for any two materials
  • n1 and n2 are the absolute refractive indices
    of the two materials

INDICES= a sign or measure of something

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12
Q
  1. Within this equation, what happens when n2 is greater than n1?
A
  • the ray will bend toward the normal
  • it does this as it enters the second material
  • ϴ1 is found between the incident ray and the ⟂
    Normal Force
  • the ray bends towards the normal n2 material
  • the n2 material is more dense
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13
Q
  1. Within this equation, what happens when n1 is greater than n2?
A
  • the ray will bend away from the normal
  • n1 = incident
  • n2 = refracted
  • the ray will bend away from the normal
  • n1 material is more dense
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14
Q
  1. What happen when n1=n2?
A
  • ϴ is the same when n1 = n2
  • the ray continues to move in the same direction
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15
Q
  1. What lies in the same plane?
A
  • the incident rays
  • the refracted (transmitted) rays
  • the normal
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16
Q
  1. What is ϴi?
A
  • the angle of incidence
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17
Q
  1. What is ϴr?
A
  • this is the angle of refraction
18
Q
  1. What is Snell’s Law?
A
  • this is the law that shows the way in which a ray
    refracts
  • this ray refracts at an interface between materials
  • these materials have indices of refraction ni and nr
19
Q
  1. How is Snell’s Law calculated?
A
20
Q
  1. What happens when light hits the surface of almost any material?
A
  • some of the light will bounce back off of the surface
  • this is known as Reflection
  • this is how we are able to see objects
21
Q
  1. What happens when light falls on a smooth surface from a particular direction?
A
  • the reflected light will also travel in a particular
    direction
  • it will travel away from the surface
22
Q
  1. What is the Law of Reflection?
A
  • this is when the reflected light leaves the surface
  • it leaves the surface at the same angle that the
    incident light falls on it
23
Q
  1. How do we calculate the Law of Reflection?
A
  • incident 2 is equal to the reflective ϴ
24
Q
  1. In which two ways can reflection be described as?
A
  1. Specular
  2. Diffuse
25
Q
  1. What is Specular Reflection?
A
  • this is what happens when light hits a surface
  • this surface is:
    - very flat
    - reflective surface
    - such as a mirror

ALL THE LIGHT COMING FROM A SINGLE DIRECTION:
- is reflected in a single direction
- parallel light rays will remain parallel after
reflection
- this is caused by a collision

26
Q
  1. What is Diffuse Reflection?
A
  • this is when the light hits a rougher surface
  • the light is reflected in a wide range of directions
27
Q
  1. What is Total Internal Reflection?
A
  • it is the complete reflection of an incident light ray at
    a boundary
  • there is no transmission
28
Q
  1. When does the phenomenon of Total Internal Reflection occur?
A
  • it occurs only for wave incidents on a boundary
  • the boundary has a medium where the reflective
    index is reduced

THERE IS NO TRANSMISSION RAY:
- when the refractive ray makes a 90° with the normal
force

29
Q
  1. What happens when the angle of incidence is larger than the critical angle?
A
  • none of the wave is transmitted through
    the boundary
  • this is when only reflection occurs
30
Q
  1. Where is the Total Internal Reflection used?
A
  • it is utilised in many optical devices
  • it can hamper efforts to see into the parts of the eye
31
Q
  1. What can be said about the Refractive Index of Real Materials?
A
  • it is not a constant for all the colours and the wavelengths of light
32
Q
  1. What is necessary for a material to be transparent?
A
  • visible wavelengths of electromagnetic radiation must
    pass through without being absorbed
33
Q
  1. Why do we see most objects in our environment easily?
A
  • the transparency in the visible wavelengths is not very
    common for solids
34
Q
  1. What happens to materials that transport to the visible light?
A
  • they will generally absorb in the wavelength bands
  • they are absorbed by these bands on either side
  • this is both in the infrared and the ultraviolet side
35
Q
  1. What varies the refractive index of a material?
A
  • it varies in a characteristic ways around the
    wavelength bands
    (infrared and ultraviolet)
  • these bands are where absorption occurs
36
Q
  1. What does an increase in the refractive index at the blue end of the spectrum result in?
A
  • the red end of the visible spectrum having a lower refractive index
37
Q
  1. What causes an increase in the refractive index at the blue end of the spectrum?
A
  • being higher on the refractive index on the shorter
    wavelength side
  • being lower on the refractive index on the higher
    wavelength side
38
Q
  1. What is Dispersion?
A
  • this is when the wave speed is depended on the
    frequency
39
Q
  1. What is Dispersive Media?
A
  • these are materials that have a wave speed that is
    depended on the frequency
40
Q
  1. What can be said about blue light?
A
  • the blue light has a higher refractive index
  • this will cause it to bend more

MED 101- PHYSICS I (28 decks)

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