Marr College
Science
Light
… and its
electromagnetic
spectrum friends
Learning Outcomes and
Summary Notes
Learning Intentions
By the end of this unit I will be able
to
1.
Carry out an investigation to show that a ray of light changes
direction when it travels from one material to another.
2. State that light changes direction when it travels from one
medium to another because the speed changes.
3. State that this change of direction due to a change of speed
is called refraction.
4. Identify the normal line on a ray diagram.
5. Complete a ray diagram to show that light bends towards the
normal as it enters glass.
6. Complete a ray diagram to show that light bends away from
the normal as it leaves glass.
7. Complete a ray diagram to show that light doesn’t change
direction if it enters the glass along the normal.
8. State three different uses of lenses.
9. Identify convex and concave lens shapes
10. Complete ray diagrams to show the paths of light rays passing
through convex and concave lenses.
11. Label the focal point on a ray diagram for a convex lens.
12. State that the light is brighter at the focal point.
13. Carry out a practical activity to measure the focal length of a
convex lens.
14. State that the image formed from the convex lens when
measuring the focal length is upside down and back to front.
15. State that the curvier a convex lens is, the shorter the focal
length will be.
16. Plan and carry out an investigation to show that a ray of white
light will split into the seven colours of the visible spectrum.
17. State that the spectrum is produced because different
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colours refract by different amounts.
18. Name the seven colours of the visible spectrum in frequency
order ROYGBIV
19. State that TV screens produce white by mixing the three
primary colours: red, green and blue.
20. State that “spectrum” is another word for “range”.
21. Identify basic parts of an eye: iris, pupil, lens, retina and optic
nerve.
22. State the function of each of the basic parts in the eye.
23. Explain how an eye can form an image on the retina for objects
at different distances. This is done by the jelly filled lens in
the eye being acted upon by muscles and becoming curvier or
thinner.
24. State that the image formed on the retina is upside down and
back to front.
25. Identify basic parts of a camera: aperture, lens and
film/detector.
26. State the function of each of the parts of the camera.
27. State that the image formed on the film/detector is upside
down and back to front.
28. State that light waves are just one part of a range of waves
called the electromagnetic spectrum.
29. State the names of the waves in the electromagnetic spectrum
in order of increasing frequency - RMIVUXG.
30. Select one of the electromagnetic waves and describe a
practical application.
31. Describe the main benefits and risks associated with one of
the electromagnetic waves (other than visible).
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Refraction
 When light moves from one material to another, its speed
changes
 This change of speed can cause a change of direction
 This is called refraction
3
Ray diagrams
The normal is a dotted line drawn at 90 degrees to the surface
at the point where the ray of light strikes.
normal
When light enters the glass, the change of direction is towards
the normal.
normal
When light leaves the glass, the change of direction is away
from the normal.
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Lenses – applications
Lenses have a large variety of applications – here are some
examples




Correcting sight – glasses and contact lenses
Telescopes
Microscopes
Projectors
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Lenses – convex and concave
A convex lens brings the rays of light together to a focal point.
The light is bright at the focal point.
The distance between the lens and the focal point is called the
focal length.
A concave lens spreads the rays of light out.
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Focal length of a convex lens
A curvier lens has a shorter focal length.
A thinner lens will have a longer focal length.
This is because a curvier lens refracts the light more.
The image formed from the convex lens when measuring the
focal length is upside down and back to front.
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Visible spectrum
When white light is passed through a triangular prism, it splits
up into the colours of the visible spectrum.
(Spectrum is another word for “range”)
Spectrum is seen because all the different colours refract
through the prism by different amounts.
Red refracts the least and violet refracts the most.
The order is ROYGBIV from least refracted to most refracted.
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Colour mixing
Red, Green and Blue light combine to give White light.
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The eye
Lens
Retina
Pupil
Iris
The image formed on the retina is upside down and back to
front.
Pupil
Hole through which light enters the eye
Iris
Controls the amount of light entering through the pupil
by contracting or relaxing
Lens
Helps to make any fine adjustments to the focusing of
the eye.
Muscles squeeze and stretch the lens to make it more
or less curvy.
Retina Sends messages to the brain through the optic nerve.
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Cameras
Parts of a Camera
The image formed on the film/detector is upside down and back
to front
•Notice that the image is upside down.
Aperture
Lens
Object
1. Old camera- Film
2. Digital cameraelectronic sensor
Aperture
Hole which lets light in.
Lens
Focuses the light in the light sensor.
Light Sensor
Detects light,
e.g. film or electronic sensor
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Electromagnetic Spectrum
Visible light is just one part of a range of waves called the
electromagnetic spectrum.
We can’t the see other waves, but they all have applications:
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Examples
Radiation
Practical
uses
Advantages
Disadvantages
Gamma rays
Used to treat
cancer
Can treat cancer
without surgery or
chemotherapy
Can cause side effects like
sickness.
Can damage healthy tissue.
Overdose can kill.
Doctors can find where
the broken bones are
and treat them
Too many X-rays can harm
your health.
X-rays
Used to sterilise
medical
equipment
Detecting broken
bones
Ultraviolet
Can treat skin
conditions like
acne
Helps to produce
Vitamin D which is
good for your skin
Overexposure to UV can
cause sunburn and skin
cancer
Visible Light
Lasers in CD
players
High quality sound
Bright visible light can
damage your eyes.
Infra-red
Street lighting
Allows us to still do
things at night
Night vision
cameras
Can see things that our
eyes can’t at night
Night vision cameras are
expensive
Remote controls
Can change TV
channels from the
couch
Remote control signal is
easily blocked
Microwaves
Heating food
Heats food quickly
Radio waves
Communication
No need for cables and
can travel around the
world
Radiotelescopes
Can see radio signals
from space
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Strong infrared can damage
your eyes
Can’t put metal in microwave
ovens
Radio reception can be poor
depending on where you live
Word list
reflection
light bouncing off surfaces
refraction
light changing speed and direction when it moves
from one medium to another
medium
another name for a material, e.g. glass, air, plastic.
prism
a triangle shaped object, made of glass or plastic,
which light rays can pass through.
normal
a line drawn at 90 to a boundary at the place where
the light ray strikes the boundary.
visible
spectrum
the range of colours of light that we can see.
convex
the shape of lens that is thin at the top and bottom
and thick in the middle.
concave
the shape of lens that is thick at the top and bottom
and thin in the middle.
electromagnetic the range of waves including visible light, from radio
spectrum
waves to gamma rays.
application
a practical use
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