Waves - reflection, refraction, v= fλ Flashcards
How do we see an object?
Light must go from the object into our eyes.
What is transmission?
When light passes from the original medium into a different medium. Often there is some reflection as well
What is an image?
What is seen when the light is bent between an object and the eye. The brain is tricked into positioning the object in the wrong place (thinking that the light is travelling in a straight line)
Law of reflection?
Angle of incidence = angle of reflection
What is the normal?
An imaginary line that is perpendicular to the reflecting surface and hits the reflection surface at the same place as the incident ray
Why are images seen?
because the brain assumes the light has travelled in a straight line from the object it is seeing
pg 122.
What happens when a reflective surface isn’t flat?
no image would be seen because the reflected rays would not all meet at the same POINT, so there would be no “position” for the tip of an object to be seen at.
What is the relationship between optical density and the speed of light?
The MORE optically dense the second medium, the more SLOWLY a light will travel in that substance and the more bent TOWARDS the normal it will be.
What is refraction?
The bending of light when it travels from one substance into another.
Why does the direction of light change when the light wave does NOT hit perpendicularly?
Because the SPEED of light changes as it goes from one medium into another, so if light strikes the boundary at an angle the direction will also change.
What is needed for an image and the object to be EXACTLY identical? (after travelling through a different medium)
The bending that happens when light enters the second medium must be EXACTLY reversed when the light leaves that medium.
This is because the surface at which light enters the second medium is PARALLEL to the surface at which the light leaves that medium. If the surfaces were not parallel the image seen would be distorted.
So the emerging ray is PARALLEL to the incident ray.
What is the wave equation?
v = fλ
v = ms^-1 f = Hertz λ = m
How is the image seen in mirror different similar to original object?
The image is
- upright
- same size
- virtual
but LATERALLY INVERTED
What happens when a surface is slightly rough?
The light rays hitting the surface would go off in different directions and therefore produce an unclear image.
If the surface is VERY rough, no image would be seen.
What is needed for a clear image?
The reflective surface must be COMPLETELY flat.
