2.4 Optics Flashcards
What is light?
Electromagnetic radiation visible to the human eye.
What do electromagnetic waves consist of?
A magnetic field and electric field travelling together displaced at 90 degrees together.
What is the pattern called that electromagnetic waves take?
Sinusoidal.
How do colours appear differently to the human eye?
Depending on the frequency or wavelength.
If the frequency of the light gets higher what will happen to the colour?
It will appear bluer and bluer until it becomes ultra violet which is the limit of the human eye.
If the frequency of the light gets lower what will happen to the colour?
It will appear redder and redder until it becomes infra-red and cannot be detected by the human eye.
How are light waves measured?
In Nanometres and Angstroms.
What range of wavelengths are visible to the human eye?
Greater than 7000Å (700nm) and less than 4000Å (400nm)
What is the speed of light in a vacuum?
186,000 miles per second.
What will change the speed of light?
The medium through which the light travels e.g. water makes it slower.
What is the formula for speed of light?
Wave x Frequency
What are the laws of reflection?
Angle of incidence is equal to angle of reflection
Incident ray, reflected ray and the normal all lie in the same plane.
What does the word plane refer too?
A two dimensional space such as a flat mirror.
What is the difference between a real and virtual image?
Real- can be projected onto screen, light waves come from an actual object
Virtual- Image appears to come from behind the mirror.
What is lateral inversion?
The effect of looking at written text in a mirror.
What are the two types of spherical mirror?
Concave and convex.
What does a convex mirror do?
De-magnify and provide a wider field of view.
What does a convex mirror do?
Magnifies the image.
What is refraction?
Change of direction in a wave when it enters another medium.
What is the refractive index?
Speed of light in a vacuum divided by the speed of light in the medium which will determine the extent of the ‘bending power’.
If the light is bent more through refraction, what does it mean?
The speed of light through the medium is lower.
What is snells law?
A formula used to describe the relationship between the angles of incidence and refraction, which gives you the refractive index.
What is convex lens also referred too as?
A converging lens
What does a convex lens do?
Used to magnify and project, the eye has a convex lens.
Convex Lens- What happens when an object is closer to the lens than the focal point?
The image is real, inverted and magnified. It produces an inverted image which is then corrected by the brain.
Convex Lens- What happens when an object is beyond the focal point?
The image is virtual, upright and magnified.
What is a concave lens referred to as?
A diverging lens.
What happens with a diverging lens?
The parallel rays are spread out so they appear to come from the focal point. The image is upright, virtual and diminished.
What are some of the advantages of fibre optics over metal wires?
Smaller and lighter
Carry more information (64,000 phone calls simultaneously)
Safer due to no electricity
What are some of the disadvantages of fibre optics?
Difficult to terminate
Difficult to repair
How is a fibre optic constructed?
High refractive core, low refractive cladding. This gives total internal reflection.
Where is the greatest loss of signal in fibre optic?
Connectors and couplings.
What is the speed of light?
3.8x10⁸ m/s
