Uses of Lenses | Physics for GCSE/IGCSE - Year 11 PDF Download

Magnifying Glasses

• If the object is placed closer to the lens than the focal length, the emerging rays diverge and a real image is no longer formed
• When viewed from the right-hand side of the lens, the emerging rays appear to come from a point on the left. This point can be found by extending the rays backwards (creating virtual rays).
• This point can be found by extending the rays backwards (creating virtual rays).
• A virtual image will be seen at the point where these virtual rays cross.

• In this scenario, the resulting image is virtual, enlarged, and upright.
  • Virtual
  • Enlarged
  • Upright
• Utilizing a lens in this manner enables it to function as a magnifying glass.
• When employing a magnifying glass, it is essential to hold the lens close to the object.

Correcting Sight

Converging and diverging lenses are frequently employed in eyeglasses to address vision impairments.

• Converging lenses are suitable for correcting long-sightedness.
• Diverging lenses are effective in rectifying short-sightedness.

Correcting Short-Sightedness

• Short-sighted individuals have eyes that are considered "too large."
• Consequently, they struggle to see distant objects clearly and can only perceive nearby objects.
• This condition arises because the eye refracts light, focusing it before it reaches the retina, which is positioned at the back of the eye.
• In essence, the focal point falls in front of the retina.
• Correction is achieved by employing a concave or diverging lens.

Correcting Long-Sightedness

• Long-sighted individuals have eyes that are deemed "too small."
• As a result, they experience difficulty in clearly seeing close objects and primarily have clear vision of distant objects.
• This occurs because the eye refracts light rays, focusing them beyond the retina at the back of the eye.
• Essentially, the focal point lies behind the retina.
• Correction can be attained by using a convex or converging lens.