Flashcards in Chapter 5 extra Deck (45):
What is one example of an electromagnetic wave?
visible light is a type of electromagnetic wave.
What is the fastest anything in the universe is able to move?
The speed of light is the fastest possible speed.
Why do you see lightning before you hear the thunder?
The light travels faster than the sound.
How does light travel?
Light travels in a straight line.
What is a wavelength?
A wavelength is the distance between a trough and the next.
What is frequency?
Frequency is the number of crests or troughs that pass a point in one second.
How do you figure out the speed of a wave?
You times the frequency by the wavelength to get the speed.
What are the colors of visible light?
red, orange, yellow, green, blue, indigo and violet
What does each color have that is unique?
Each color has its own wavelength.
Which color has the longest wavelength?
Red has the longest wavelength and the lowest frequency
Which color has the shortest wavelength?
Violet has the shortest wavelength and the highest frequency
What kind of light is not visible to humans?
Ultraviolet light is not visible to humans, xrays are also not visible, infrared light and radio waves also cannot be seen
How can you see infrared light?
Infrared light can be seen with night vision goggles
How can you know there are radio waves around you?
You can hear them on your radio.
What is the electromagnetic spectrum?
The electromagnetic spectrum is the visible light waves, plus all those that we cannot see.
What are the primary colours?
Primary colours are red, green and blue
What are secondary colours?
magenta, cyan and yellow
What makes magenta?
magenta is made from blue and red
What makes cyan?
cyan is made with blue and green
What makes yellow?
green and red make yellow.
When all the primary colours are combined what is the colour of the light?
White light is a combination of all primary colours.
How does the human eye see colour?
Humans have photoreceptor cells which are sensitive to long, medium and short wavelengths.
Why are we able to see many different shades of green and not red?
Green is in the middle of the visible light spectrum, which makes it easier for our eyes to see.
What is reflection
Reflection is when light travels through one material and bounces off another.
When light bounces off a surface what happens to its direction?
Light bounces off in a straight line, it doesn't curve.
What is the angle of incidence?
The angle of incidence is the angle of incoming light.
What is the normal?
The normal is the perpendicular (straight up and down) imaginary line to the surface.
What is the angle of reflection?
The angle of reflection is the angle between the reflected light and the normal (imaginary line)
What is spectacular reflection?
Spectacular reflection is where all the light is reflected in the same direction. The image that is reflected looks the same as the original image
What is diffuse reflection?
Diffuse reflection is when light reflects off a rough surface. The normal points to different spots, so the reflected light goes in different directions.
At night car headlights sometimes produce diffuse reflections and other times spectacular reflections, why is this possible?
The road surface is rough, but puddles of water are smooth. Off puddles the reflection is spectacular (perfect) and off the road it would be diffuse.
What is refraction?
Refraction is when light travels into a new material (medium) and the material slows the light down so it changes its' angle.
What is the index of refraction?
Each material has an index of refraction which tells us the amount the light will bend.
If you have two materials n1 and n2, and light travels slower in n2, which way will the light bend?
The light will leave n1 and enter n2, then the light will slow down and bend towards the normal center line.
If you have two materials n1 and n2 and light travels slower in n1, which way will the light bend when it enters n2
when the light enters n2 it will speed up and bend away from the normal center line.
How is reflection different than refraction?
The angle of refraction that the light bends to does not have to be equal to the angle it entered the new material, but in reflection the angle of incidence will be equal to the angle of reflection
What is a lens?
A lens is an optical device made of plastic or glass.
What happens to light when it passes through a lens?
A lens will refract light and change its' direction.
What is a convex lens?
A convex lens curves outwards.
What is a concave lens?
A concave lens curves inwards.
What happens when two beams of light strike a lens that is convex on both sides? (a double convex lens)
The light is refracted inwards and is said to converge
What is the focal point?
The focal point is the point where beams of light cross.
What happens when two beams of light strike a lens that is concave on both sides? (biconcave lens)
the light is refracted outwards and is said to be diverging.
What happens to light when it goes through a prism?
The light is refracted at different angles and each light wave slows down so is split and it becomes a rainbow.