Geometric Optics and Optical Instruments

Set created for Science Olympiad Div. B Optics.

What are the three types of reflection?

Spectral, diffuse, and fresnel

What is the difference between geometric optics and wave optics?

Geometric optics deals with situations including objects several times larger than the wavelength of light at hand, while wave optics deals with wavelength sized things.

What is refraction? What law governs it?

The bending of light due to a change in velocity when it changes media. It is governed by snell’s law.

What is specular reflection?

Reflection that occurs for flat and shiny objects, for example mirrors.

What is diffuse reflection?

Reflection that occurs for dull and rough objects, and is the reason why we can see things.

What is fresnel reflection?

Reflection that occurs when only a portion of the light is reflected and the rest is refracted.

What is the law of reflection?

The angle of incidence is equal to the angle of reflection.

When light travels from a FASTER medium to a SLOWER medium in refraction, how does it bend?

Towards the normal.

When light travels from a SLOWER medium to a FASTER medium, how does it bend?

Away from the normal.

What is total internal reflection?

When light is reflected inside a medium instead of being transmitted to the next medium.

What are the requirements that must be met for total internal reflection to occur?

The first medium must have a greater index of refraction than the second and the angle of incidence must be greater than the critical angle.

What is the critical angle?

The angle at which TIR will occur for a specific set of media.

What does TIR stand for?

Total internal reflection.

What is dispersion?

The process by which a beam of white light is separated into a spectrum of colors when it refracts in certain media.

Why does dispersion occur?

Dispersion occurs because for shorter wavelengths there are greater refractive indexes, and this is exacerbated in some media.

What is index of refraction? How is it denotated in equations?

Index of refraction is the degree to which the speed of light changes in a medium. It is denoted as n in equations.

Are convex lenses converging or diverging?

Converging.

Are concave lense converging or diverging?

Diverging.

How can you tell if a lens/mirror is converging or diverging?

If it is converging, rays of light will come together at the focal point. If it is diverging, the rays will appear to originate at the focal point.

Are convex mirrors converging or diverging?

Convex mirrors are diverging mirrors.

Are concave mirrors converging or diverging?

Concave mirrors: Converging.

What kind of image do convex mirrors form?

Convex mirrors form virtual, upright, and diminished images.

What are optical fibres?

Plastic or glass tubes used to convey light across great distances.

How are optical fibres used?

For communication and medical purposes.

How do optical fibres move light along curves?

They utilize total internal reflection to move light along curves.

How do optical fibres make sure that the conditions for TIR are met?

Optical fibres are coated with a substance that ensures that n2 < n1, and their aperture is so small that light will probably not enter at less than the critical angle.

What is a real image?

A projected image in front of a mirror.

How do you know if an image is a real image?

If the image distance is positive, then it will be a real image.

What is a virtual image?

An image that appears to be located behind a mirror.

How can you tell if an image is virtual?

If the image distance is negative, then the image is virtual.

How can you tell if an image is magnified or reduced?

If the magnification is greater than 1, it is magnified. If it is less than 1, it is reduced.

How can you tell if an image is inverted?

If the magnification is negative, then an image is inverted. If it is positive, it will be right side up.