Light

Question 1

Wavelengths of light.

Answer 1

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

Question 2

Is light a wave or a particle?

Answer 2

Light has both wavelike and particle like behaviours.

Question 3

Light travels in straight lines is known as…

Answer 3

Linear propagation

Question 4

Light particles are called…

Answer 4

Photons

Question 5

How does light act like a particle?

Answer 5

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

Question 6

Formula relating energy to frequency.

Answer 6

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

Question 7

What is an electron volt?

Answer 7

Equivalence of one electron with a volt of energy.

J/1.60x10^-19=eV

Question 8

Speed of light is what?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

Lowest energy wave and their use

Answer 10

Radio waves, communication and entertainment.

Question 11

Applications of microwaves

Answer 11

Microwave (the appliance), phone calls

Question 12

Infrared waves uses

Answer 12

TV remotes

Night vision and infrared cameras

Question 13

What did Newton contribute to theories on visible light?

Answer 13

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

Question 14

UV light applications.

Answer 14

Bug zappers.

Question 15

Gamma ray uses.

Answer 15

Destroying cancer growths.

Question 16

Universal Wave Equation

Answer 16

v=f λ

Question 17

__________ bodies emit light.

Answer 17

Luminous.

Question 18

___________ bodies give off light by reflection.

Answer 18

Illuminated.

Question 19

____________ bodies emit light under certain conditions.

Answer 19

Incandescent.

Question 20

Natural sources of light.

Answer 20

Stars, lightning, northern lights, bioluminescent animals.

Question 21

Transparent materials do what?

Answer 21

Allows passage of light in straight lines.

Question 22

Opaque materials do what?

Answer 22

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

Question 23

Translucent materials do what?

Answer 23

Allows passage of light but in different directions.

Question 24

Spectra of light. 3 things.

Answer 24

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).

Question 25

Intensity of light equation.

Answer 25

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).

Question 26

Refraction.

Answer 26

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

Question 27

Absolute index of refraction equation.

Answer 27

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

Question 28

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

Answer 28

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).

Question 29

relative index of refraction.

Answer 29

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.

Question 30

Snell's law.

Answer 30

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).

Question 31

Why are cut diamonds so sparkly?

Answer 31

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.

Question 32

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

Answer 32

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

Question 33

At what point does total internal reflection occur?

Answer 33

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

Question 34

How is the critical angle found?

Answer 34

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) ```

Question 35

SALT for flat mirror reflection.

Answer 35

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

Question 36

Steps for raytracing of flat mirror.

Answer 36

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).

Question 37

What is the principle axis line?

Answer 37

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

Question 38

What is the vertex of a mirror?

Answer 38

The geometric center of the reflecting surface (labeled V)

Question 39

What is the center of curvature.

Answer 39

Center of the spherical reflecting surface (Labelled C).

Question 40

What is the radius of curvature?

Answer 40

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

Question 41

What is the principle focus?

Answer 41

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)

Question 42

What is the focal length?

Answer 42

Distance between Focus and Vertex.

Question 43

What is the focal plane?

Answer 43

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

Question 44

Characteristics of concave mirrors (SALT).

Answer 44

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

Question 45

Characteristics of convex mirrors (SALT).

Answer 45

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

Question 46

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

Answer 46

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).

Question 47

What aspect of images changes from mirrors to lenses?

Answer 47

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.

Question 48

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

Answer 48

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.

Question 49

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

Answer 49

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. ```

Question 50

What is spherical aberration? How is it solved?

Answer 50

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.

Question 51

What is chromatic aberration. How is it solved?

Answer 51

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).