Optics

Getting good study habits

What is a wave?

A disturbance or movement that transfers energy through a matter of space

What are examples of waves?

Water wave, sound wave, microwaves

What is energy?

The capacity to apply a force over a distance

What is force?

A push or pull

What is a crest?

The highest point of a wave

What is a trough?

The lowest point of a wave

What is a wavelength?

The distance (in meters) for one complete cycle of the wave (Example: Crest to crest or trough to trough)

What is amplitude?

The height of a wave crest or depth of a trough, as measured from its rest place

What is medium?

The matter that waves travel through

What are two types of waves that can travel through a medium?

A transverse wave and a compression wave

What is a transverse wave?

A transverse wave is where energy in the medium moves perpendicular to the direction of the wave

What is a compression wave?

A compression wave is when matter in the medium moves parallel to the direction of the wave

What is frequency?

The number of repetitive motions or oscillations that occur in a given time

How do you measure frequency?

Hertz (Hz)

What happens when the frequency of a wave increases?

The wavelength decreases

What is the equation for frequency?

Frequency = cycles/seconds

What is light?

A wave that travels through empty space

What is visible light?

Light energy you can see

What is an example of light energy being transferred from one location to another?

Sun -> earth

What is refraction?

The bending of waves due to a change in its speed

When do light waves refract?

When they pass from one medium to another

What is white light made up of?

Different wavelengths

The longer the wavelength, the ______ it will refract (smaller angle)

Less

The shorter the wavelength, the ____ it will refract (greater angle)

More

When white light is separated into different colours, what is the band of colours called?

The spectrum

What colours are easiest to see on the spectrum?

Red, orange, yellow, green, blue, indigo, violet (ROYGBIV)

What does nm stand for?

Nanometers

What colour has the longest wavelength?

Red (700 nm)

What colour has the shortest wavelength?

Violet (400 nm)

What is white light?

The result of mixing together all the different colours of light

What causes white light to split into a spectrum?

A prism

What happens when white light hits a prism?

All the colours that the white light is composed of will refract at different angles, producing a spectrum of colours

When does reflection occur?

When light bounces off an object

What happens when white light strikes an object?

Some colours are reflected some are absorbed (only the reflected colours can be seen)

Example: What happens when white light hits a yellow shirt?

Yellow is reflected and the other colours are absorbed

What is an example of white light?

Sunlight

What happens when light passes from air to water?

The water refracts the light

What is happening when you are looking at a black shirt?

The shirt is absorbing all the light

The higher the frequency the more it ____________

Refracts

What is the spectrum of radiation called?

The electromagnetic spectrum

What types of radiation are on the spectrum, in order from lowest frequency to highest frequency?

Radio waves, microwaves, infrared waves, ultraviolet waves, x-rays and gamma rays

What are radio waves used for?

Listening to the radio, MRI tech to see inside body

What are microwaves used for?

Cooking, telecommunications, tracking motion, weather forecasting, taking pictures of earth

infrared waves used for?

Record differences in temperature, remote controls, infrared cameras

What is visible light used for?

Everything, so we can get around, see, do things

What are ultraviolet waves used for?

When UV rays hit your skin, you make vitamin D

What are x-rays used for?

To photograph teeth/bones, detect cracks in metal, photograph the inside of machines

What are gamma rays used for?

Radiation therapy to kill cancer cells

Wavelengths shorter than visible light have________________

More energy than visible light

What is another way to describe light?

As a particle (Photons)

What is the ray model of light?

A straight line, or ray, to show the direction the light is travelling

What are the three things light can do?

Transmit, absorb and reflect

What is transparent material?

A material that allows light to pass through it freely

What are examples of transparent materials?

Clear glass, air, water

What is translucent material?

Materials that let most light through but scatters light leaving

What are examples of translucent material?

Clouds, waxed paper, lampshades

What is opaque material?

Materials that prevent light from passing through

What are examples of opaque material?

A metal can, a wall, a book

When is a shadow created?

When an opaque object absorbs light rays

What does a shadow demonstrate?

That light travels in a straight line

What does a ray diagram show?

How the distance from the light source affects the size of the shadow an object makes

What is the incoming light ray called?

The incident ray (i)

What is the ray that bounces off the surface called?

The reflected ray (r)

What is the normal?

An imaginary line perpendicular to the surface

How do you measure the angle of incidence?

It is measured from the normal to the incident ray

How do you measure the angle of reflection?

It is measured from normal to the reflected ray

What is the law of reflection?

The angle of incidence equals the angle of reflection

What is refraction?

The bending of light, due to a change in speed

What causes light to change direction?

A change in speed (When light travels from one transparent medium to another transparent medium, it changes speed)

How do you measure the angle of refraction (R)

It is measured from the refracted ray to the normal

If light rays slow down as they refract (ex. moving from gas to liquid), the light rays bend toward the normal.

If light rays speed up as they refract (ex. moving from liquid to gas), the light rays bend away from the normal.

Why do objects in water appear in a different location than they actually are?

Because of refraction

What happens when light passes through air at different temperatures?

It refracts

What is a mirage?

The light from the sky bending as it approaches the warm air near the ground

What is a flat smooth mirror called?

A plane mirror

Plane mirrors form an image that appears to be as far ___________ the mirror as the object is in front of it

Behind

Left and right appear to be _______________ in a plane mirror.

Reversed

What is a concave mirror?

A mirror that curves inward

What is a focal point?

Light reflecting off a concave mirror that meets at a single point

What are converging rays?

light rays that come together

What happens if an object is far away (behind the focal point) from the concave mirror?

It appears small and upside down

What image is formed on a concave mirror?

It depends on the location of the object

As the object moves closer towards the mirror (between focal point and mirror), the image will become ________________________________

Larger and upright

What are some examples of concave mirrors?

Flashlights, car headlights, shaving, make-up mirrors

What is a convex mirror?

A mirror that curves outward

What happens to light rays that hit a convex mirror?

They diverge & don't meet

What are diverging rays?

Rays that are going away from each other and don't touch

What are the two characteristics of images formed by a convex mirror?

1. Objects appear to be smaller than they are
2. More objects can be seen in an object mirror than a plane mirror

What are some examples of convex mirrors?

Security mirrors, rearview or sideview mirrors on cars

What is a lens?

A piece of transparent material that can bend or refract light rays in useful ways that can help form a well focused image

What are the two things lenses can be?

Convex or concave

What are concave lenses?

They are thinner in the middle than at the edge

What kind of image does a concave lens produce?

It produces images that are upright and smaller than the object

What does a concave lens cause light rays to do?

Diverge

What are some uses of concave lenses?

Near sighted eyewear and telescopes

What are convex lenses?

Lenses that are thicker in the middle than at the edge

What do convex lenses cause light rays to do?

Converge

What happens when parallel rays strike a convex lens?

They come together at the focal point

What are examples of convex lenses?

A magnifying glass