Topic 3.2 - Light Flashcards
What happens when rays of light hit a plane mirror?
They are reflected.
What are the characteristics of an image formed from a plane mirror?
- The same size as the object
- On the the same side of the mirror as the object
- An inverted (upside down) version of the object
When light is reflected how do angles i and r compare?
angle of incidence = angle of reflection
How are the angles of incidence and reflection measured?
Relative to the normal.
What is a virtual image?
An image produced on the same side of the lens as the object.
What is a real image?
- An image produced on the opposite side of the lens from the object.
- A real image can be formed on a screen as the light rays cross after the lens.
What kind of image is produced by a plane mirror?
A virtual image.
What is refraction?
- Refraction is the change in speed of a wave crossing a boundary between two media, resulting in a change in direction.
Which property of a wave is not changed by refraction?
The frequency
What is the critical angle?
The angle of incidence which produces an angle of refraction of 90°
What is internal reflection?
When light rays reaches a boundary and some of the rays are reflected back into the medium which it came from.
What is total internal reflection?
When a ray of light is fully reflected back into the medium it came from, when reaching a boundary between media.
When does total internal reflection occur?
When the angle of incidence is greater than the critical angle.
Define refractive index
The ratio of the speed of light in a vacuum to the speed of light in any given medium.
Give the equations for refractive index
When light passes through a converging lens…
The light rays bend towards the normal, and meet at a focal point.
What is the principal focus of the lens?
A focal point before a convex lens, from wich light rays appear to come from, or the focal poiny afdter a concave lens where all the rays meet.
Draw a diagram of light rays through a converging lens
How can lenses act as magnifying glasses?
By producing an enlarged, virtual image.
How does wavelength affect refraction?
Shorter wavelength waves refract more
What happens when white light is shone through a prism?
It separates into a spectrum of all its coloured light components.
Why is white light separated by a prism?
Each different coloured light wave has a different wavelength. The shorter wavelength lights like blue refract more while the light with the longest wavelength red refracts the least. This creates a spectrum
List, in the correct order, the colour spectrum produced by the dispersion of white light
Red, orange, yellow, green, blue, indigo and violet.
What is monochromatic light?
- Light that has a single frequency
- A laser light is an example of a monochromatic light
What are the conditions for total internal reflection?
- The light is travelling from an optically denser medium (higher refractive index) to an less optically dense medium
- The critical angle is exceeded
What do Optical Fibre do?
Optical fibres transmit light by total internal reflection.
What are the key features of an optic fibre?
- Core
- Cladding
- Protective Coating
What are optical fibres used for?
- Internet providers use optical fibres to set up quick and reliable internet connections.
- They can be used for endoscopy
Do optical fibre lose lots of information?
No they don’t they are able to transmit huge amounts of information with few information losses
What is the focal length?
The focal length is the distance from the centre of the lens to the principal focus
What is the principal focus?
- Light rays that are parallel to the optical axis pass through the lens and converge (come together) at the principal focus.
- There is one principal focus on each side of the lens as light can pass through the lens in either direction.
What is the image produced by a conveging lens like when the object is more than two focal lengths from the centre of the lens? and Draw it
- The image is real
- The image is inverted
- The image is diminished (smaller than the object)
- Image is between F and 2F
- Examples: the eye and cameras
What is the image produced by a conveging lens like when the object is between one and two focal lengths from the centre of the lens?
- The image is real
- The image is inverted (upside down)
- The image is magnified (larger than the object)
- Examples are the projector and the photocopier
What is the image produced by a conveging lens like when the object is two focal lengths from the lens
- The image is the same size as the object
What is the image produced by a conveging lens like when the object is between the principal focus and the centre of the lens?
- The image is erect (the right way up)
- The image is Virtual
- The image is magnified
- The image is also on same side of the lens as the object
- Am example is a magnifying glass
What is the dispersion of light?
- Dispersion is the seperation of white light into a spectrum (range) of colours
- A rainbow is an example of a spectrum that is formed when sunlight is dispersed by raindrops.
What is the refractive index of air
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