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Physical Science 20 > Light > Flashcards

Light Flashcards

1
Q

Wavelengths of light.

A

Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma Ray.

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2
Q

Is light a wave or a particle?

A

Light has both wavelike and particle like behaviours.

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3
Q

Light travels in straight lines is known as…

A

Linear propagation

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4
Q

Light particles are called…

A

Photons

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5
Q

How does light act like a particle?

A

It can cause electrons to be emitted (such as solar panels).

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6
Q

Formula relating energy to frequency.

A

E=hf
E is energy in joules
h is Planck’s constant (6.63x10^-34 Js)
f is frequency in hertz

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7
Q

What is an electron volt?

A

Equivalence of one electron with a volt of energy.

J/1.60x10^-19=eV

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8
Q

Speed of light is what?

A

300,000,000m/s
Or
3.00x10^8m/s

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9
Q

How are EM waves similar to ocean waves? How are they different?

A

Both carry energy. EM waves don’t need a medium to travel through.

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10
Q

Lowest energy wave and their use

A

Radio waves, communication and entertainment.

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11
Q

Applications of microwaves

A

Microwave (the appliance), phone calls

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12
Q

Infrared waves uses

A

TV remotes

Night vision and infrared cameras

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13
Q

What did Newton contribute to theories on visible light?

A

He showed that white light is not coloured by a prism, but was separated into different colours.

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14
Q

UV light applications.

A

Bug zappers.

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15
Q

Gamma ray uses.

A

Destroying cancer growths.

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16
Q

Universal Wave Equation

A

v=f λ

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17
Q

__________ bodies emit light.

A

Luminous.

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18
Q

___________ bodies give off light by reflection.

A

Illuminated.

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19
Q

____________ bodies emit light under certain conditions.

A

Incandescent.

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20
Q

Natural sources of light.

A

Stars, lightning, northern lights, bioluminescent animals.

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21
Q

Transparent materials do what?

A

Allows passage of light in straight lines.

22
Q

Opaque materials do what?

A

Transmit no light (unless material is very thin). Reflect some of the light that falls on them and absorb the rest.

23
Q

Translucent materials do what?

A

Allows passage of light but in different directions.

24
Q

Spectra of light. 3 things.

A

Continuous spectrum, all colors are present within white light.
Absorption spectrum, some elements absorb certain colors (black bands) and reflect everything else (like light passing through a dust cloud).
Emission spectrum, light is only produced as certain wavelengths (colored bands).

25
Q

Intensity of light equation.

A

I = P / 4 Pi R^2
I: intensity, a measure of power over the area.
P: power.
Pi: ratio of any circle’s circumference to its diameter.
R: radius. (Radius is really the distance between the light and object).

26
Q

Refraction.

A

The change of direction of light as it passes from one medium to another.

27
Q

Absolute index of refraction equation.

A

n = c / v

n: index of refraction.
c: speed of light in a vacuum.
v: velocity of light in the medium.

28
Q

What happens to light as it reaches a boundary between two mediums?

A

Partial reflection: some light waves are passed through to the next medium

Partial refraction: the light that passes through to the next medium will refract (towards or away from the normal).

29
Q

relative index of refraction.

A

1n2 = n2/n1

1n2: relative index of refraction. if >1, bend towards normal, light slows down. if <1, bend away from normal, light speeds up. if =1, no change in refraction or speed.

n2: where the light ends up.
n1: where the light begins.

30
Q

Snell’s law.

A

n1 sin(i) = n2 sin(R)

n1: initial material.
n2: end material.
i: incident angle.
R: refracted angle.

if R is undefined, there is no refraction. (only possible when travelling from slower to faster mediums).

31
Q

Why are cut diamonds so sparkly?

A

They have high indexes of refraction and are cut so that light will go through internal reflection many times before being scattered, leading to a sparkly appearance.

32
Q

How do you find relative index of refraction using the angle of incidence and refraction?

A

1n2 = sin(i) / sin(R)

33
Q

At what point does total internal reflection occur?

A

When the incident ray’s angle is greater than the critical angle.

34
Q

How is the critical angle found?

A

n1 sin(i) = n2 sin(R)

R = 90

n1 sin(i) = n2 sin(90)
n1 sin(i) = n2 * 1
sin(i) = n2 / n1
i = sin^-1(n2/n1)
i = sin^-1(1n2)
35
Q

SALT for flat mirror reflection.

A

S: No magnification / no change in size.
A: Erect.
L: Behind the mirror (opposite of the object).
T: virtual.

36
Q

Steps for raytracing of flat mirror.

A

1: locate the image (draw it on the opposite side of the mirror).
2: draw a line from eye to image.
3: draw a line from the object to the point of incidence of the previous line.
4: Draw the normal line.
5: measure the angle of incidence and reflection (they should be equal).

37
Q

What is the principle axis line?

A

The line that passes through the vertex and center of curvature of a curved mirror.

38
Q

What is the vertex of a mirror?

A

The geometric center of the reflecting surface (labeled V)

39
Q

What is the center of curvature.

A

Center of the spherical reflecting surface (Labelled C).

40
Q

What is the radius of curvature?

A

Distance from the center of curvature to the mirror (R)

41
Q

What is the principle focus?

A

The point on the principle axis line where light rays travelling parallel to the axis line pass through, or seem to pass through.
Halfway between V and C. (V/2)

42
Q

What is the focal length?

A

Distance between Focus and Vertex.

43
Q

What is the focal plane?

A

A perpendicular line that holds any foci that exist from converging rays.

44
Q

Characteristics of concave mirrors (SALT).

A

S: Larger or smaller.
A: Erect or Inverted.
L: Behind or in front of the mirror.
T: Real or virtual.

45
Q

Characteristics of convex mirrors (SALT).

A

S: Always smaller (like a passenger-side mirror).
A: Always erect.
L: Always behind the mirror.
T: Always virtual.

46
Q

Describe the 3 rays used to locate an image with a curved mirror.

A
  1. Passes through focus - Reflects parallel.
  2. Travels parallel to axis - reflects through focus (or appears to).
  3. Travels through C - reflects back. (Might not pass through C on the incident, but a continuation of line intersects C).
47
Q

What aspect of images changes from mirrors to lenses?

A

Real images are on the same side of the mirror as the object.
Real images are on the opposite side of the mirror as the lense.

48
Q

Describe the 3 light rays used to locate an image for lenses.

A

Convex lenses:

  1. Ray hits the center and passes straight through.
  2. Ray passes through F’ and travels parallel after lense.
  3. ray travels parallel to the axis, ray travels through F.

Concave lenses:

  1. Ray hits the center and passes straight through.
  2. ray travels parallel to the axis, reflecting as it came from F’.
  3. Ray heading towards F, ray travels parallel after lense.

F is opposite side of lense as object.
F’ is same side of lense as object.

49
Q

1/do + 1/di = 1/f and hi/ho = -di/do = M

A

Finds the focus or a mirror or lense, or the distance of an object from the mirror/lense, or the distance of an image from the mirror/lense.

if d is positive, image is real (unless it’s a lense).
Remember that f for lenses is on the opposite side than the object.

h is height
d is distance
i is image
o is object
M is magnitude
f is focus.
50
Q

What is spherical aberration? How is it solved?

A

An optical problem that occurs when all incoming light rays end up focusing at different points after passing through a spherical surface.

Cheap way to solve it is to cover the outer edge of the mirror.
Proper way to solve it is to use a parabolic shape instead of a spherical one.

51
Q

What is chromatic aberration. How is it solved?

A

The more spherical the shape of the lense, the more different light waves are refracted.
This causes dispersion of colour.

Solved by using an additional part to bend waves back together at the focal point. (Two different types of glass, like crown and flint).

Physical Science 20 (6 decks)

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