Light Flashcards
What is the Law of Reflection?
i = r
angle of incidence = angle of reflection
(Practical) How do you investigate reflection?
- Use a vertically upright plane mirror.
- Mark out a dotted line on the paper for a normal
- Label the intersection of the normal and mirror as ‘x’
- Switch the ray box on, direct it to point ‘x’
- measure i and r
- repeat!
What are the properties of a mirror image?
- sizes are the same
- distance from plane mirror is the same as distance from the virtual image
- Image is laterally inverted.
Refraction of Light
Refraction is when light experiences a change of speed at the boundary of two optical media.
(Practical) Investigating Refraction:
- Place a glass block on a sheet of paper
- trace along it
- Use a ray box to shine a light through the glass back at the normal (control)
- Use another one to shine a light through the glass block at an angle
- trace the incident ray and refracted ray
- choose various angles.
What is Snell’s Law?
sin i / sin r = constant
What is the refractive index?
n = c / v
n = speed of light in a vacuum / speed of light in the medium
speed of light = 3.0 x 108m/s
What is total internal reflection?
Total internal reflection can only occur when an optically denser medium to a less dense medium.
What is a critical angle?
The critical angle is the angle of incidence for which the angle of refraction - to a less dense medium - is 90o
If the angle of incidence is larger than the critical angle, total internal reflection occurs.
What equation can help find the critical angle?
n = 1 / sin c
How is total internal reflection applied?
- Glass Prisms
- Optical Fibres (light does not escape even if bent. higher carrying capacity, ;less signal degradation, cheaper)
What determines the path of light through a lens?
Converging Lenses (Thicker at the Center): eye-shaped; half-eye shaped; beginning bracket
Diverging Lenses (Thinner at the center): Pillar-like; outer straight bracket; outer bracket
Parts of Thin Converging Lenses
Principal Axis: horizontal line through the center
principle focus: where all the rays converge
focal length: distance between C and F
optical centre: midpoint of surfaces of the lens
focal plane: passes through focal point, perpendicular to the principal axis.