The video tutorial explains vision defects, focusing on short-sightedness and long-sightedness. Short-sightedness is caused by an elongated eyeball or a powerful lens, corrected with diverging lenses. Long-sightedness results from a short eyeball or weak lens, often due to aging, corrected with converging lenses. The power of lenses is calculated using the formula p = 1/f, with diverging lenses having negative power. Laser eye surgery is a permanent solution, reshaping the cornea to focus light on the retina.

What is a common cause of short-sightedness?

• The eyeball is too short.

• The lens is too weak.

• The cornea is reshaped.

• The eyeball is elongated.

How can short-sightedness be corrected?

• Using a converging lens.

• By reshaping the cornea.

• Using a diverging lens.

• By strengthening the lens.

What is a typical reason for long-sightedness?

• The lens is too powerful.

• The cornea is reshaped.

• The eyeball is elongated.

• The eyeball is too short.

What type of lens is used to correct long-sightedness?

• Converging lens

• Bifocal lens

• Diverging lens

• Concave lens

What is the power of a diverging lens with a focal length of -0.15 meters?

• 6.67 dioptres

• -6.67 dioptres

• -0.15 dioptres

• 0.15 dioptres