using lenses to correct vision

Purpose of cornea

Bend light towards lens

Once the cornea has bended light towards the lens…

The lens refracts the light, focusing it on the retina and forming an image.

What happens if the cornea is too thick or too curved?

Light is refracted too much → lens will focus light in front of instead of on the retina.

What will happen if light is focused in front of the retina?

a blurry image will be formed

If someones eyeball length is too long are they short sighted or long sighted?

Short sighted

If someones eyeball length is too short are they short sighted or long sighted?

Long sighted

Lenses to correct short sightedness

Concave (diverging) lens

Lenses to correct long sightedness

Convex (converging) lens

What does the concave lens do to light before it reaches the cornea?

Spreads it outwards

What does the convex lens do to light before it meets the cornea?

Bends it closer together/ towards cornea

Both lenses ensure that light is focused…

On the retina, forming a clear image

For distant objects, does the lens get thicker or thinner?

Thinner

For near objects, does the lens get thicker or thinner?

Thicker

Journey light takes from source to retina

Source —> lens (concave/convex) —> cornea —> lens —> retina

“Describe how lenses in glasses can correct long-sightedness”

• long sightedness: eyeball is too ____, causing light to be _______ behind the ____.

• We use a ______ (converging) ___ to fix this.

• The convex lens _____ light more ______ cornea.

• Cornea bends light onto ____.

• Lens is then able to refract and ____ this light on the ______.

Short, focused, retina, convex, lens, refracts, towards, lens, focus, retina