Optics Flashcards
What is light?
Electromagnetic radiation which is visible to the human eye
What do electromagnetic waves consist of?
A magnetic field and an electric field traveling together
What angle are magnetic fields and electric fields displaced at to each other?
90˚ following a sinusoidal pattern
The colour of light that can be perceived by the human eye are actually differences in?
Frequency or wavelength of the electromagnetic waves falling onto the retina
What colour does light go with a higher frequency of light?
Blue
When the frequency of light is too high for humans to see what happens to it?
It becomes ultra violet
What colour does light go with a lower frequency of light?
Red
What happens to the light when the frequency becomes too low?
It becomes infra-red
Can humans see ultra violet or infra-red?
No
What are light waves measured in?
Nanometres and angstroms
In nanometres what is the scale that humans can see in wavelengths?
400nm-700nm
Light is a type of?
Wave
What is the speed of light in a vacuum?
186,000miles per second or 300,000,000 metres per second
What happens to light speed when it travels through water, glass, and diamonds compared to a vacuum?
It gets slower
When light passes through matter the speed is?
Reduced
What is the equation for speed of light?
Wavelength x frequency
In an equation If the speed of light is not given to you what must you do?
Assume its traveling in a vacuum at 3x10^8 m/s
What is reflection?
That a light wave bounces back when it hits a different medium
The angle of incidence is equal to?
The angle of reflection
The incident ray, reflection ray, and normal all lie within?
The same plane
In relation to reflection what is does the word plane refer to?
A two-dimensional space
What are the two ways an image can be created by a reflection?
Real or virtual
What is a real image?
Can be projected onto a screen or wall
What is a virtual image?
An image that can only be seen looking into the optics and cannot be projected
When a plane mirror is used what happens to the formed image?
-its the same size
-virtual image
-same distance behind as in front
-back to front but right way up
What are the two types of spherical mirrors?
Concave and convex
What direction does a convex mirror curve?
Outward, towards the light source
What type of spherical mirror is used to make the image appear smaller?
Convex
What type of spherical mirror is used to provide a wider field of view?
Convex
What direction does a concave mirror curve?
Inwards, away from the light source
What happens to an image if it is close to a concave mirror?
-magnified
-upright
-virtual
What happens to an image if it is far away from a concave mirror?
-diminished
-inverted
-real image
What is refraction?
Change in direction of a light wave when it enters a different medium
Why does refraction happen?
When light crosses the boundary between two mediums, the change in speed causes the light to change direction
What is the only exception for refraction not to take place?
When the ray is perpendicular to the surface (light changes speed but not direction)
What is the refractive index of a material?
The ratio of the speed of light in a vacuum compared to the speed of light in the material
What does a bigger refractive index mean?
The more light will bend when entering and leaving the material
What is the equation for the refractive index?
Speed of light in a vacuum over the speed of light in the material
What is snells law?
A formula used to describe the relationship between the angles of incidence and refraction
What is a lense?
An optical device that refracts light
What is a lense used for?
To form an image
How do lenses form images?
The same way as curved mirrors but by refraction rather than reflection
What are convex lenses also referred to as?
A converging lens
What is special about the thickness of a convex lens?
It is thicker at its centre compared to the edges
What type of image does a convex lens form?
A real or virtual image depending on the positions of the object and the observer
What is a concave lens also referred to as?
Diverging lens
What is special about the thickness of a concave lens?
It is thinner at its centre
What image is formed by a concave lens?
Always upright, virtual, and diminished
What does fibre optics transmit?
Light through fibres
How does fibre optic cables work?
The information is converted to a light signal and transmitted along a fibre at the speed of light. Once at the end the signal is reconverted into information
How big is a fibre optic strand?
The same as a piece of hair
What are fibre optic strands made from?
Glass or plastic
What are the advantages that fibre optics have over metal wires?
-lighter and smaller
-carry more information
-intrinsically safer
What are the main disadvantages of fibre optic?
Difficult to terminate and difficult to repair due to size
Why does fibre optic strands have a core with a high refractive index?
So all the light is reflected back into the fibre
Why does a fibre optic strand have cladding with a low refractive index?
So as little light is lost
What is internal reflection?
The core and cladding strengths in a fibre optic cable
Where is the greatest loss of signal occur in fibre optics?
At connectors and couplings
