Electromagnetic Spectrum Flashcards
On a ray diagram what is the normal line?
It’s the line drawn at right angles to the barrier or mirror
Where is the incident Ray and reflected Ray measured from?
The normal
What letter represents the angle on incidence?
I
What letter represent the angle of reflection?
R
Go to page 66 and look at Ray diagrams
Yolo
What is the law of reelection?
When waves are reflected, the angle of reflection is equal to the angle of incidence
When does light travel in different speeds?
In different materials, it travels faster in air than it does in water or glass.
When a ray of light moves into a material where it travels at a different speed, it usually changes direction. What is this called?
Refraction
When is there no change in direction?
When light meets the interface (boundary) at right angles (along the normal)
When light passes from water or glass or air with small angles of incidence most of the light passes through the interface but a little is reflected. As the angle of incidence increases, the angle of refraction also increases until the refracted light passes along the interface. If the angle of incidence increases further, the light is completely reflected inside the glass. What is this called?
Total internal reflection and the angle of incidence at which starts to happens is called the critical angle
What is a ray diagram?
It’s a way of modelling what happens when light is reflected or refracted
What happens when a small amount if light goes through a different material?
Some of its reflected but most of its refracted
What happens when the angle of incidence equals the critical angle?
The refracted light passes along the interface (boundary) of the glass block
What happens when the angle of incidence is greater than the critical angle?
The light is completely reflected inside the block
When you swim underwater, you may be able to see reflections on the underside of the water. What are these caused by?
Total internal reflection
How can we investigate refraction?
By measuring the angles between the light rays and the normal. The light ray approaching the interface is called the incident Ray. The angle between this Ray and the normal and the light Ray leaving the interface is called the angle of refraction
When do you see luminous objects?
When light from them enters your eyes. You see non luminous objects because they reflect light
Most materials have rough surfaces if you examine them closely, so the reflected light is scattered in all directions. What is this called?
Diffuse reflection
Very smooth surfaces such as mirrors reflect the light evenly, what is this called?
Specular reflection
What is the light from the sun or lamps called?
White light
What is white light?
White light is a mixture of different colours of light that our eyes see as white
What can white light be split up into using a prism?
The colours of the visible spectrum
What happens when white light hits a coloured surface?
Some of the colours that make it up are absorbed and some are reflected
Theatres use spotlights to produce effects on stage. Spot lamps produce white light but how can they be coloured?
Using filters
What are filters?
They are pieces of transparent material that absorb some if the colours in white light
Why do you see different colours?
Because you have three types of cone cells in the parts of your eyes that detect light (the retina). Each cone detects red, green or blue light which are the primary colours of light (nit the same as the primary colours of paint). If red cones and green comes both detect light, you see the light as yellow. If all three sets of cones Derek t light, you see it as white
Hat is a lens?
A piece of transparent material shaped to refract light in particular ways. The power of a lens describes how much it bends light that passes through it. A more powerful lens is more curved and bends the light more
What is a converging lens?
It’s the fatter in the middle than at the edges. It makes parallel Ray’s of light converge (come together) at the focal point and the centre of the lens.
What is a diverging lens?
It is thinner in the middle than at the edges. The focal points if the point from which the rats seem to be coming after passing through the the lens, they go apart at the focal point
Go to pg 72 and 73
And look at the diagrams
What. Does the kind of image formed by a covering lens depend on?
Where the object is