P3.2.1 & 3.2.3 - Reflection & Lenses Flashcards
What is reflection? [2]
occurs when a light ray strikes a shiny surface and bounces back in a straight line.
What are the laws of reflection? [2]
- The angle of incidence is equal to the angle of reflection
- The incident ray, the reflected ray and the normal all lie in the same plane
What type of surface does reflection always happen on? [1]
Smooth surface
What happens if light is reflected from a rough surface? [1]
Scattering of light - goes in all directions
What is a normal? [2]
The line at right-angles to a mirror’s surface
What are the rules for image size and position when a plane mirror forms an image? [3]
- The image is the same size as the object
- The image is as far behind the mirror as the object is in front
- A line joining equivalent points on the object and image passes through the mirror at right-angles
Where is the angle of incidence and angle of reflection always measured from? [1]
The normal
How much will the sum of angles between a plane mirror and the normal always be? [1]
90 degrees
What is the angle of incidence equal to? [1]
the angle of reflection
What is the critical angle? [2]
the angle of incidence at which the angle of refraction is 90degrees and above
What is total internal reflection? [2]
- when angle of incidence in denser medium is bigger than critical angle
- the ray gets completely internally reflected
What is a principle axis? [2]
- a line passing through the centre of the lens
- perpendicular to the axis of the lens
What is a principle focus? [2]
- the point where parallel rays coming from distant object meet after they pass through the lens
What is focal length? [2]
- distance from the centre of the lens to the principle focus
