Physics chapter 13 Flashcards
What is the speed of light?
300,000km/s
How do we see things?
When light is reflected off of the item and into or eyes
What is a luminous object?
An object that produces light
What is a non-luminous object?
An object that reflects light
Properties of light?
. Travel in a straight line
. Travels faster than sound
. We see things when light is reflected into out eyes
. Shadows are created when an object blocks the light
What are the two laws of reflection?
- Incident ray, reflected ray, and the normal to the reflecting surface lie on the same plane
- The angle of incidence and the angle of reflection are equal
Define virtual image?
A copy of an object formed at the location from which light rays appear to come
Define real image?
The image which is formed when the light rays meet at a particular point after reflection from the mirror
What is the main difference between real and virtual image?
The real image can be obtained on the screen whereas the virtual image cannot be obtained on the screen.
Properties of images formed in a plane mirror?
. The same size as the object
. The same distance behind the mirror as the object in front of it
. Left and right are inverted
. Virtual
Define ray diagram?
A diagram showing the path of rays of light
Define sharp real image?
An image that can be displayed on the screen
How is a sharp real image formed?
When all rays from one point on an object arrive at a unique point of the image
Define refraction of light?
The bending of light as it passes from one transparent substance to another
In which direction does light refract when moving from a low density substance to a higher-density substance (Air to Water)?
It would reflect towards normal
In which direction would light refract when moving from a high-density substance to a low density (Water to Air)?
It would move away from normal
The formula for refractive index (n)?
Speed of light in vacuum / Speed of light in material
Sin i / Sin r
Formula for Snell’s law?
Sin i / Sin r
i= Angle of incidence
r= Angle of refraction
Define total internal reflection?
The complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.
What condition has to be met for total internal reflection to happen?
The angle of incidence must exceed the critical angle
Explain why diamonds are so shiny?
Because diamond has a very low critical angle of 25⁰, this allows the light to easily achieve total internal reflection
Formula for finding critical angle?
n = 1/sin C
What are fibre optics/optical fibres?
The medium and technology are associated with transmitting information as light pulses along a glass, plastic strand, or fibre.
What is fibre optics used for?
For long distance and high-performance data networking
What material must be used for fibre optics?
High-purity glass must be used in telecommunications as any impurities used can absorb the light.
How does light travel inbside optical fibre?
Light travels along by total internal refelction.
It bounces along the inside of the fibre as each time it strikes the inside, the angle of incidence is greater than the critical angle, thus no light is lost and all of it is reflected.
Give an example of Fibre optics being used in medicine?
They are used in endoscopes.
What is the purpose of an endoscope?
An endoscope is a device that can be used to see inside the paitiens body
How does an endoscope operate?
One bundle of fibres carries light down into the body and another bundle is used to carry the image back up to the user. It may also have a small cutting tool built in to perform minor operation.
What is another name for convex lense?
Converging lense
What is another name for concave lens?
Diverging lenses
How does concave lens affect the light?
Concave lens causes all rays to diverge. Concave lenses create only virtual images. After the rays are refracted they never converge, and no real image is formed.
Define optical focus of a lens?
The centre point of a lens
Define principal Axis of a lens?
A line passing through the oprical centre
Define focus in lens?
The point where rays converge after refraction in lens.
Define Spectrum (Plural - Spectra)
Waves or colors of light seperated out in a order according to their wavelengths
Define dispersion?
The seperation of different wavelengths of light because they are refracted through different angles.
Define ray box.
Apparatus used to produce a ray of light
Define ray.
A narrow beam of light
Define laser?
A device for producing a narrow beam of light of a single color (monochromatic) or wavelength.
Define incident ray?
A ray of light arriving at the surface
Define reflected ray?
A ray of light which has been deflected from a surface.
Define normal.
The line drawn at right angles to a surface at the point where a ray hits the surface
Define image.
What we wee when we view an object by means of reflected rays
Define laterally inverted.
An image in which left and right have been reversed
Define refractive index.
The ration of the speeds of a light wave in two different media
Define enlarged.
Used to describe an image which is larger than the object
Define diminished.
Used to describe an image which is smaller than object.
Define critical angle.
An angle of incidence that gives a reflection of 90 degrees.
Define total Internal Reflection.
Reflection in a more dense material where there are no refracted rays.
