Download Optics Test – Science 8 Introduction to Optics 1. What are some

Optics Test – Science 8
Introduction to Optics
1. What are some devices that you use in everyday life that require optics?
Light Energy and Its Sources
308-8 identify and describe properties of visible light
1. What is light?
Light is a form of energy that can be detected by the human eye. Light cannot be touched or
tasted, but it can warm things up so it gives heat energy to objects.
2. What is energy?
Energy is the ability to do work. Energy can be neither created nor destroyed. Energy can only
be transformed from one form to another.
3. Where does light energy come from?
Light energy comes from two different sources, natural and artificial.
4. What is the most important source for natural light?
The sun is the most important source for natural light.
5. What is the difference between luminous and non-luminous objects?
Objects that emit (give off) their own light are called luminous. Objects that do not emit light,
but reflect it from other sources are called nonluminous.
6. What are some examples of luminous objects?
7. What are some examples of nonluminous objects?
8. Why is the Moon nonluminous?
The Moon is nonluminous because it reflects light from the Sun
9. What are some common forms of luminous energy?
Chemical, electrical, nuclear, thermal
10. List the different sources of light.
1. Light from Incandescence – Incandescent source means the process of giving off light
because of the high temperature. Light produced by a flame, candle, campfire, or light bulb.
2. Light from Phosphorescence – Some materials, called phosphors, give off light for a short
time after you shine a light on them. They store the energy and then release it as light
energy.
3. Light from Electric Discharge – An electric discharge is the process by which a gas releases
light because of electricity passing through it.
4. Light from Fluorescence – The release of light from a substance caused by exposure to
radiation from an external source.
5. Light from Chemiluminescence – Chemiluminescene is the process of changing chemical
energy into light energy with little or no change in temperature.
6. Light from Bioluminescence – some living things, such as fish, can make themselves
luminous using a chemical reaction like chemiluminescence.
11. What are the properties of light?
Light travels in a straight line (rectilinear propagation).
Light travels at a speed of 300 000 km/s in air.
Reflection
Refraction and dispersion
Light travels in a vacuum and in some other types of media
Getting in Light’s Way
308-9 Describe the laws of reflection of visible light and their applications in everyday life
1. What is Transparency?
Transparency is the measure of how much light can pass through a material. Materials can be
classified as transparent, translucent or opaque.
2. What is the difference between transparent, translucent and opaque?
Transparent – let light pass through easily
Translucent- let some light pass through, but also reflect some light
Opaque – Do not allow any light to pass through
3. When does reflection occur?
Some materials reflect light. Reflection occurs when a ray of light is returned after hitting a
surface.
4. What three properties affect the amount of light reflected or absorbed?
Colour, sheen and texture are three properties that describe the amount of light energy
absorbed or reflected.
• Colour – Black and dark-coloured materials absorb a lot of light when compared to white and
light coloured materials.
• Sheen – dull materials, such as wood, absorb more energy than shiny materials, such as
aluminum siding.
• Texture – A rough textured object will absorb more light energy than a smooth surface.
5. Why do black and dark coloured materials absorb more light energy than white and light
coloured material?
Light does not reflect off dark coloured objects instead the light gets absorbed by the dark
coloured object.
Inquiry Investigation: Reflecting Light off a plane Mirror
308-9 Describe the laws of reflection of visible light and their applications in everyday life (regular vs.
diffuse, angle of incidence = angle of reflection)
208-7 Formulate operational; definitions for incidence, reflection and the normal
209-2 Estimate angles of incidence and reflection
1. What colours are contained in white light?
White light contains all the colours of the rainbow (ROY G. BIV)
2. Why is an apple red?
1. All the" invisible" colors of sunlight shine on the apple.
2. The surface of a red apple absorbs all the colored light rays, except for those corresponding to
red, and reflects this color to the human eye.
3. The eye receives the reflected red light and sends a message to the brain.
3. What is regular reflection?
The reflection of light off a smooth, shiny surface.
4. What is diffuse reflection?
When light hits an irregular surface, reflected light scatters in many directions.
5. What happens to light when it reflects off a rough surface?
When light reflects off a rough surface the light reflects in all directions, so very little light will
defect.
6. How much light does an ordinary mirror reflect?
An ordinary mirror reflects about 90% of the light that falls on it perpendicularly
7. How much light is reflected from a sheet of glass?
A sheet of glass reflects about 8% of the light that falls on it. That is why windows sometimes
behave like mirrors and reflect an image of the room.
8. Why is diffuse light easier on your eyes than other types of reflected light?
Diffuse light is easier on your eyes because the light is reflected and scattered in many
directions. Direct light and glare strains your eyes. Diffusion is found in homes, schools and
places of work.
9. What are plane mirrors?
Plane mirrors are regular flat mirrors
10. What is reflection?
Reflection occurs when a ray of light is returned after hitting a surface.
11. What is an incident ray?
An incident ray is a light ray that strikes a surface. When light strikes a reflecting surface, it
bounces off the surface.
12. What is a reflected ray?
A reflected ray is the light that is reflected from a surface.
13. What is the normal?
A reference line that is perpendicular (90 degrees) to the reflecting surface at the point where
the incident ray strikes the surface.
14. What is the angle of incidence?
The angle between the incident ray and the normal is called the angle of incidence, i.
15. What is the angle of reflection?
The angle between the normal and the reflected ray is called angle of reflection, r.
16. What is the largest possible angle of incidence for a light ray traveling toward a mirror?
The largest possible angle of incidence is 90 degrees.
17. What is the smallest possible angle of incidence?
The smallest angle of incidence is 0 degrees. When this happens no bending occurs.
Reflecting Light Off Surfaces
1. What are the 2 laws of reflection?
1. The angle of reflection, r, is always equal to the angle of incidence, i.
2. The incident ray, the normal, and the reflected ray are always in the same plane.
Inquiry Investigation: Curved Mirrors
209-2 Estimate angles of incidence, reflection and focal length.
209-6 & 211-1 Work co-operatively and collaboratively to plan and safely construct an optical device
using mirrors.
210-14 Identify and correct practical problems in the way a constructed optical device functions.
1. What are spherical mirrors?
Spherical mirrors are concave and convex mirrors.
2. What are Convex mirrors?
Convex mirrors are silvered on the outside. They have a reflecting surface on the outside curve,
like the back of a spoon.
3. How are images formed from a convex lens?
Images formed from a convex lens are inverted, or upside down.
4. What are Concave mirrors?
Concave mirrors are silvered on the inside. They have the reflecting surface on the inside of the
curve, like the inside of a spoon.
5. What is a focal point?
The focal point of a convex lens is the point where light rays parallel to the axis are brought to a
point; it is not where the image is formed.
6. What is the focal length?
The distance from the focal point to the middle of the mirror.
Inquiry Investigation: The Refraction of Light
308-10 & 210-11 Describe qualitatively how visible light is refracted
208-1 Rephrase questions related to refraction in a testable form
208-5 Predict the effect of transparent media on the angle of refraction of light
209-2 Estimate angles of refraction
1. What is refraction?
The bending of light as it travels from one material into another.
2. What is the angle of refraction?
The angle between the refracted ray and the normal
3. What happens when light hits a transparent surface?
When light hits a transparent surface, most of the light enters the material. If light strikes the
surface at an angle, it changes direction upon entering. Once light crosses the boundary
between the two materials, it continues to travel in a straight line. For this reason, refraction is
called a “ boundary behavior”.
4. If you found a coin in the water, would you reach for the exact location the coin appears to be?
Explain your answer.
Refracting Light in Lenses
1. Why does light refract?
The light refracts because the speed of light through different materials changes. When light
passes from air to the more dense glass, it slows down. The change in speed also causes a
change in direction.
2. What happens to the light ray when it passes through air and then glass?
If a light ray passes from a less dense substance such as air into a denser substance such as
glass, it will bend towards the normal.
3. What happens when a light passes from glass to air?
When light passes from a denser to a less dense material, it will bend away from the normal.
The amount of refraction depends on the angle of the incoming ray.
4. Why do birds diving for fish usually enter the water at right angles?
Birds dive at right angles perpendicular to the water’s surface so their vision is not distorted.
The Visible Light Spectrum
1. What is the visible spectrum?
The band of colours in a rainbow is called the visible spectrum (we can see those colours). It has
six main colours called the spectral colours. From top to bottom - ROY G. BIV (Red, Orange,
Yellow, Green, Blue, Indigo and Violet)
2. How did they discover that white light is made of spectral colours?
It used to be thought that we could see colour because objects had colour in them. In 1666,
Isaac Newton thought that sunlight might be made of several colours. He took a glass prism and
passed a beam of sunlight through it. The beam on the other side was made of the spectral
colours.
3. What did Newton discover about coloured light in a prism?
Newton also discovered that each colour acts differently inside a prism. Light actually travels at
different speeds in the prism, causing each colour to refract a little differently. The colour that
refracts the most is violet.
4. Which waves in the visible spectrum have a greater frequency (happen more often)?
5. Which waves have the biggest wavelengths?
6. Which waves require more energy?
The Electromagnetic Spectrum
308-11 describe different types of electromagnetic radiation, including infrared, X-rays, ultraviolet,
microwaves and radio waves
308-12 compare properties of visible light to the properties of other types of electromagnetic radiation,
including infrared, X-rays, ultraviolet, microwaves and radio waves
113-2 Describe possible negative and positive effects of technologies associated with electromagnetic
radiation
109-13 Explain the importance of using the words frequency and wavelength correctly
1. What is radiant energy? Radiant energy is energy transferred or emitted as waves or rays in
all directions. Light is a form of radiant energy that you can see. However, the visible part
that you can see is only a small part of the range of radiant energies.
2. What is a radiant?
A radiant is energy that is sent out in the form of waves or rays. Other radiant energies are
microwaves, UV rays (ultraviolet radiation), infrared, radio waves and X rays.You cannot see
these other radiant energies, but they are of the same kind as light.
3. What is the electromagnetic spectrum?
The whole range of radiant energies is called the electromagnetic spectrum.
4. What is radiation?
Radiation is the heat transfer of radiant energy waves or rays such as light.
5. How is energy transmitted as a wave?
Energy can be transmitted as a wave. Waves with short wavelengths have more energy,
because more energy is needed to create them.
6. Can the magnetic spectrum travel through space as well?
Light and other parts of the electromagnetic spectrum can travel at very high speeds. In a
vacuum, such as space, the speed is 300 000 km/s. It takes light 1.3s to get from the Earth to
the moon.
7. Be able to give general characteristics of the electromagnetic spectrum.
(radio, microwave infrared, visible, ultraviolet, X-ray, gamma ray)