2.4 Optics Flashcards
What colour the higher the frequency
Bluer ther light becomes until it turns Ultra Violet
What sort of wave is Light
electromagnetic
What colour the lower the frequency
The redder it will appear until its turn Infra Red
Light waves have very small wavelengths and they are measured in Nanometres and Angstroms. What are thier values?
1 Nanometre (nm) = 1 × 10−9 m
1 Angstrom (Å) = 1 × 10−10 m or 0.1 nm
Wavelengths greater than or 700 nm and less than or 400 nm will be
Invisible to the eye
Speed of Light in a vacuum
186 000 miles per second
or
300,000,000 metres per sec (3 x 10^8 m/s)
Speed of Light through water
224 000 kilometre per sec
Speed of Light through Glass
200 000 kilometre per sec
Speed of Light through Diamond
124 000 kilometre per sec
Formula for speed of light
speed of light = wavelength x freq
In a flat mirror, the angle of incidence =
The angle of reflection
The image created by a mirror or lens can be
real or virtual
For plane mirrors, the image formed is:
- the same size as the object
- as far behind the mirror as the object is in front
- virtual
- laterally inverted or back to front but the right way up.
There are two types of spherical mirrors:
concave and convex.
Define a convex mirror?
curves outward, toward the light source. The reflected rays from a convex mirror diverge, making the image appear smaller and providing a wider field of view.
Define a concave mirror?
curves inwards, away from the light source. If the object is close to the mirror, a magnified, upright and virtual image is formed, whereas if the object is far from the mirror, a diminished, inverted and real image is formed. Concave mirrors may be found in make-up kits and dentists tools, to provide a magnified view.
What is refraction
The change in direction of a wave when it enters a different medium i.e Water, However, when the light ray is perpendicular to the surface it changes speed but not direction.
What is refractive index? And the formula…?
The refractive index of a material is the ratio of the speed of light in a vacuum compared to the speed of light in the material. The bigger the refractive index the more light will bend when entering and leaving the material.
n = c / v
* n = refractive index
* c = speed of light in a vacuum
* v = Speed of light in the material (m/s)
What is Snell’s law used for?
Its a formula used to describe the relationship between the angles of incidence and refraction. From this relationship it is possible to determine the refractive index of a material by looking at the angle of refraction.
How do lenses work for images?
Lenses form images in much the same way as curved mirrors but by refraction rather than reflection.
Define a convex lens?
Also referred to as a converging lens, its thicker at its centre than at the edges. A convex lens may form either a real or virtual image depending on the positions of the object and the observer.
Define a Concave Lens?
A concave lens, also referred to as a diverging lens, is thinner at its centre. The image formed by a concave lens is always upright, virtual, and diminished.
What are Fibre optics made from
A fibre is a hair-thin strand of glass or plastic
Fibre optics have certain advantages over metal wires, what are they?
- Lighter and Smaller
- Able to carry more info
- Instrinsically safer
Disadvantage of Fibre Optics
Difficult to terminate
What does a fibre optic core have?
High refractive index
What does the cladding of a fibre have?
A low refractive index
