section 2 lights science

ray diagrams

show how light travels.

• a ray of light is represented by a straight arrow

intensity

the intensity (brightness) of light changes with distance. Fewer rays hit your eyes as you move away from a light source

how light interacts with materials

transparent- all light passes through

translucent- some light passes through

opaque- no light passes through

luminous

objects that produce light

non-luminous

objects that do not produce light. Light reflects off of them and travels to our eyes

regular reflection

when parallel light rays hit a smooth surface. Light rays reflect at the same angle

diffuse reflection

when parallel light rays hit a rough surface. Light rays reflect at different angles and are scattered

plane mirrors

plane mirrors are flat mirrors. When a ray of light hits a plane mirror at an angle, it reflects off the surface at the same angle

normal

the line perpendicular to the mirror at the point of reflection

angle of incidence

the angle between the incident (incoming) ray and the normal

angle of reflection

is the angle between the reflected ray and the normal

law of reflection

the angle of incidence equals the angle of reflection

focal point

• the point at which parallel light rays converge after reflecting off a mirror

• when light reflects off a mirror, an image is formed where the reflected rays converge

real images

formed when light actually converges

virtual images

formed when light appears to have converged on the other side of the mirror.

apparent light rays are drawn with dotted lines on a ray diagram

concave mirrors

a mirror that curves inward. reflected rays converge at a focal point in front of the mirror

convex mirrors

• a mirror that bulges outward.

• reflected rays spread outward

• a virtual image is formed where the apparent light rays converge behind the mirror

refraction

when light bends as it moves from one transparent medium to another

• a beam of light will bend because it changes speed when it moves into a substance with a different density

• light moves more slowly through substances that are more dense

• the greater the change in density, the greater the refraction

incident ray

before bending, the ray is called the incident ray

refracted ray

after bending, the ray is called the refracted ray

lens

a curved piece of transparent material.

when light rays pass through a lens, they refract

concave lens

a lens that is thinner in the middle than at the edges

convex lenses

a lens that is thicker in the middle than at the edges.

light rays converge (come together) at a focal point