Author Question: A farsighted person has a near point distance greater than the normal distance of 25 cm. Neglecting ... (Read 86 times)

2125004343 · **on:** Jul 28, 2018

A farsighted person has a near point distance greater than the normal distance of 25 cm. Neglecting the eye-lens distance, which approach will yield an appropriate corrective lens for this condition?
1.The corrective lens should have a focal length equal to the normal near point distance, i.e., 25 cm.
2.The corrective lens should have a negative focal length equal in magnitude to the normal near point distance, i.e., 25 cm.
3.The corrective lens should make an object at a distance equal to the near point appear to the eye to be at a distance of 25 cm.
4.The corrective lens should make an object at a distance of 25 cm appear to the eye to be at a distance of the near point.

Question 2

Camera 1 has a lens of diameter 2.0 cm with a focal length of 5.0 cm, camera 2 has a lens of diameter 1.5 cm with a focal length of 4.5 cm, and camera 3 has a lens of diameter 1.1 cm with a focal length of 3.3 cm. Assuming all the cameras use the same type film and have a shutter speed of 1/200 s, which camera can give the best exposure at the lowest light level?
1.3
2.2
3.2 and 3 are both equal and better than 1.
4.1