Optics and Light Lenses form images by refracting light

Refraction of Light  As light waves travel through a medium that slows the wave down, they turn toward the normal (imaginary line perpendicular to the new surface).  Light waves that travel through a medium that speeds up the waves, they turn away from the normal.  Draw diagram of this on page 600 of textbook in the next slide.

Shape determines how lenses form images  A lens is a clear optical tool that refracts light.  Different lenses refract light in different ways and form images useful for a variety of purposes.  Like mirrors, lenses can be concave or convex.

Concave Lenses  Concave lenses are curved inward.  Parallel light rays that pass through a concave lens are refracted outward.  The light rays are refracted twice and are spread out, therefore they do not meet.  Draw the concave lens found on page 601 on the next slide.

Diagram of Concave Lens * A concave lens causes parallel light rays to spread out.

Convex Lenses  Convex lenses are curved outward.  Parallel light rays passing through are refracted inward and meet at a focal point on the other side of the lens.  The light rays are refracted twice.  Draw the convex lens found on page 601 in the textbook on the next slide.

Convex Lens  A convex lens causes parallel light rays to meet at a focal point.