May
21
Converging lenses questions–10pts reward!?
ByI’m having trouble with my physics lab questions. Can someone help me on these please??
1- In terms of focal length, how far behind the camera lens is the film located when very distant objects are being photographed?
2- Why do older people who do not wear glasses read books farther away from their eyes than do young people? What changes occur w/ respect to the eye’s focal length after many years?
3- What equipment you would need to collect virtual image data using converging (convex) lens? Where should I place the object, and what characteristics of the image would be expected?
2 Comments
May 21st, 2011 at 9:41 pm
for 1.distance between the screen and lens is varied by moving the lens and not screen. 2.i’ve already answered. 3.the object should be placed between focus and the optical centre of the lens.
May 21st, 2011 at 9:41 pm
1. (There’s no implication in this question of what moves and what doesn’t.) The film is at the focal distance of the lens.
2. Older eyes tend to become farsighted; that is the focal point of the cornea plus lens lies in back of the retina, due to lens or eyeball shape change or a combination of the two. Also, accommodation (the ability to adjust the lens’s focal length) decreases. Converging lenses (reading glasses) are needed for close-up vision, to bring the image onto the retina.
3. The object is on the other side of the converging lens from your eye or the camera and its distance from the lens is less than the focal distance. The image will appear larger than the object. Since a virtual image can’t be captured directly on a screen, it must be looked at or photographed.