Mirrors

Mirrors

Drawing a ray diagram for an image in a plane mirror:

• The image is the same size as the object
• It's as far behind the mirror as the object is in front
• It's formed from diverging rays, meaning it's a virtual image

How...

• Firstly draw the virtual image, not the rays, following the rules that it's the same size and as far behind the mirror as the object is in front
• Then draw a reflected ray going from the top of the virtual image to the top of the eye - a bold line between the eye and the mirror but a dotted line between the virtual image and the mirror
• Next draw the incident ray going from the top of the object to the mirror, the incident and the reflection rays follow the laws of reflection but measuring the angles isn't necessary. Draw the line from the top of the object to the point where the reflected ray meets the mirror
• Now do steps 2 and 3 again for the bottom of the eye - reflecting ray going from the image to the bottom of the eye and the incident ray going from the object to the mirror

Curved mirrors:

• Concave mirrors are shiny on the inside of the curve
• Convex mirrors are shiny on the outside of the curve
• Light shining on a concave mirror converges
• Light shining on a convex mirror diverges
• Uniformly curved mirrors are like a round portion of a sphere, the centre of the sphere is the centre of curvature
• The centre of the mirror's surface is called the vertex
• Halfway between the centre of curvature and the vertex is the focal point
• Rays that come in parallel to the normal axis reflect and meet at the focal point
• The centre of curvature, vertex and focal point all lie on the line…