Light and the Eye

Unit Review Sheet

Facts and Definitions

Lesson 1: Lines of Light

• Reflection occurs when light waves hit an opaque surface and bounce back.
• Some objects, like the Sun, are luminous, meaning they give off their own light. Others, like the Moon, are non-luminous, meaning they reflect light from their surface but don't give off their own light.
• The angle of incidence is the angle of an incoming light ray.
• The angle of reflection is the angle of an reflected light ray.

Lesson 2: Translucence and Shadow

• Opaque means that light cannot pass through an object.
• Transparent means that light can pass through an object.
• Translucent means that some light passes through an object, but objects on the other side cannot be seen clearly.
• The penumbra is the lightest part of a shadow, around the edge.
• The umbra is the darkest part of a shadow, in the middle.

Lesson 3: Refraction and Lenses

• Refraction is a process in which the path of light is changed as it passes from one transparent material to another.
• A lens is a piece of transparent material used to alter the paths of rays of light passing through it.
• Concave lenses or mirrors have surfaces that curve inward. They are thinner in the middle and thicker around their edges.
• Convex lenses or mirrors have surfaces that curve outward. They are thicker in the middle and thinner around their edges.

Lesson 4: How Human Eyes Work

• The cornea is the clear outer layer of the eye. It lets light into the eye and helps the eye focus.
• The iris is the colored part of the eye. It has muscles that adjust the size of the pupil to allow more or less light into the eye.
• The pupil is the black circle at the center of the iris. In dim light, the pupil gets larger to let more light in; in bright light it gets smaller to let less light in.
• The lens bends light rays onto the retina.
• At the back of the eye, the retina interprets light rays into images.
• The retina contains cells that respond to light entering the eye. They are divided into two types: rods — which detect shape, movement, and light in shades of gray — and cones, which detect colors.
• The optic nerve sends information from the retina to the brain.

Lesson 5: Animal Eyes

• Predators are animals that catch and eat other animals. Prey are animals that are eaten by other animals.
• Binocular vision is the ability to use two eyes, slightly offset from each other, to perceive distance accurately.

Lesson 6: Color and Perception

• The colors of a rainbow are red, orange, yellow, green, blue, indigo, and violet.
• The visible spectrum is the visible portion of the electromagnetic spectrum.
• The color reflected by an object makes it appear that color to our eyes. For example, green objects reflect green light but absorb the other six colors.
• White objects reflect all seven colors. Black objects absorb all seven colors.

Final Project: Tools of the Eye

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