Week 1

Question 1

Laws of Reflection

Answer 1

Reflection is when light waves bounce off a reflective surface and travel in a new direction.
Laws:
1. The reflected light ray is in the same plane as the incident ray and the normal to the surface
2. The angle of reflection equals the angle of incidence

Question 2

Principle of Reversibility

Answer 2

If an object is placed at the focal point, then the light reflected by the mirror will be focused at infinity

Question 3

what is the image formed by a concave mirror where the object is located outside the centre of curvature?

Answer 3

The image will be real, inverted and minified

Question 4

What is the image formed by a concave mirror where the object is located in between the centre of curvature and the focal length?

Answer 4

The Image will be real, inverted and magnified

Question 5

What is the image formed by a concave mirror, where the object is located within the focal length?

Answer 5

The image will be virtual erect and magnified

Question 6

What is the image formed by a convex mirror ( object places anywhere on axis)

Answer 6

The image will always be virtual erect and minified for an image formed by a convex mirror no matter where the object is placed.

Question 7

Gonioscopy and total internal reflection

Answer 7

• The critical angle of air cornea interface is 46 degrees.
• the incident angle of light reflected from the angle is greater than the critical angle and causes total internal reflection.
• direct and in-direct goniolenses eliminate total internal reflection and offer clear visualisation of the anterior chamber angle
• the refractive index of the goniolens is close to the corneal refractive index , allowing light to enter inside the lens instead of causing total internal reflection
• light rays are further reflected by a mirror and and light exits the lens at 90 degrees to the goniolens interface

Question 8

Refraction

Answer 8

the amount of refraction will vary at different heights from the optic centre ( spherical aberration)
The amount of refraction will vary with different wavelengths ( chromatic aberration)
when light is refracted, blue light is refracted the most (short wavelength) and red wavelengths the least ( longer wavelengths)

Question 9

Paraxial Optics

Answer 9

Paraxial Optics provides a simplified form of Snell’s law of refraction. It only considers the rays closest to the optic axis and not the peripheral rays. Sin theta can be treated as a small angle in radians. Therefore under this assumption n Sin theta = n’ Sin theta’ becomes n theta = n’ theta’

Question 10

Image magnification

Answer 10

M>1 = magnified
M<1 = minified
M is negative = real and inverted
M positive = virtual and erect