NOT DONE!!!! Chapter #13 - Light Flashcards
What way do light waves travel?
In straight lines.
What is the normal?
The normal is drawn 90 degrees to the mirror.
What is the incident ray?
A ray of light arriving at the surface.
What is reflected ray?
A ray of light which has been reflected from a surface.
What is the i angle?
The angle of incidence: The angle between the incident ray and the normal drawn at the point where the ray hits the surface.
What is the r angle?
Angle of reflection: The angle between the reflected ray and the normal drawn at the point where the ray hits the surface.
What is the law of reflection?
The angle of incidence and the angle if reflection are equal (i=r)
Draw a diagram of a mirrior and an object.
What type of image is a reflection?
A virtual image
What are the properties of an object reflected in a plane mirror?
- The image is the same size as the the object
- The image is the same distance behind the mirror as the object is in front of it.
- it is laterally inverted = left and right are reversed
- It is virtual
What is a virtual image?
An image that cannot be formed on a screen
When does the ray bend towards the normal?
When the ray enters a denser substance.
When does the raybend away form the normal?
When the ray enters a less dense object
Why is light refracted?
Because it travles at different speeds in different materials.
How do you measure how much light is bent?
By calculating the refractive index.
What is the defenition of the refractive index?
The ratio of speeds of a light wave in two different media.
What is the defenition of internal reflection?
When a ray of light strikes the inner surface of a material and some of it reflects inside it.
What is the defenition of critical angle?
The minimum angle of incidence at which total internal reflection occurs
When does total internal reflection occur?
When the angle of incidence is greater than the critical angle.
What is the critical angle of:
* water
* glass
* diamond
Water: 49
Glass: 42
Diamond: 25
What makes the critical angle smaller/bigger?
The greater the refractive index of the material, the smaller the critical angle and vice versa.
What is the equation for the refractive index?
n = sin i / sin r
What is the equation for the critical angle?
n = 1 / sin c
Draw a labled diagram of a converging lense with the rays.
What are some of the uses of lenses?
- Spectacles
- Cameras
- Microscopes
- Telescopes
How does a converging/concave lens look?
How does a diverging/biconcave lens look?
Principle focus
In a converging lens
Where the rays are concentrated together
How does the focal length varry?
Depending on the thickness. The thicker the converging lens, the shorter the focal length.
Enlarged
Used to desceibe an image that is bigger than the object.
Diminished
Used to decribe an image which is smaller than the object.
Inverted
Used to decribe an image which is upside down compared to the object.
Principal axis
The line passing through the center of a lense perpendicular to its surface.
Converging lens
A lens that causes rays of light parallel to the axsis to converge at the principal focus.
Diverging lens
A lens that causes rays of light parallel to the axis to diverge from the principal focus.
What are the features of the lenses in our eyes?
- They are flexible
- Muscles can change the shape and strength of the lens
What does having flexible lenses in ours eyes help with?
It allows us to focus on objects at different distances.
Why do some people need an extra lens for their eyes (contact lenses and glasses)?
Because some eyes are unable to change their strength enough to focus on either close or distant objects.
Short sight
A person with short sight can see close objects clearly but not distant objects. The image forms in front of the retina.
Long sight
Can focus on distant objects but not close ones. This is because the eyeball is too short and/or the lens cannot become strong enough so the rays from a close object cannot be converged enough to form a clear image on the retina.
What is the order if the spectrom least refracted to most?
- Red
- Orange
- Yellow
- Green
- Blue
- Indigo
- Violet
Spectrum
Waves, or colors of light, separated out in order according to their wavelengths.
Dispersion
THe seperation of different wavelengths of light because they are refracted through different angles.
