I need help with these few questions. Thanks!! 1. I take two pictures of my dog
ID: 1267743 • Letter: I
Question
I need help with these few questions. Thanks!!
1. I take two pictures of my dog Kaycee. I use the same film and level of illumination for both pictures, but I double the f-number for the second picture. By what factor will the required time of exposure change if the film is to receive the same total light energy?
2. A 1.5 m tall woman stands 5.0 m in front of a camera with a 4.0 cm focal length lens. What is the size of the image formed on film?
3. A camera lens is initially set at f/16 for a shutter speed of 1/60 s. If the amount of lighting on the subject is unchanged and the lens is set at f/5.6, what is the proper shutter speed at this setting?
4. A person's prescription for bifocals is -0.25 diopter for distant vision and +2.50 diopters for near vision, the near vision being accomplished by inserts into the distant vision lens. What is the net power of the near vision correction?
5. What must be the resolving power of a grating allowing a spectral line at 601.10 nm to be distinguished from another line differing by 0.38 nm? (1 nm = 10-9 m)
Explanation / Answer
1.9.0
2.
3. The first opening diameter of the lens is = 1/16 of the focus length
The second opening diameter of the lens = 1/5.5 of the focus length
Compare the two opening diameters:
(f/5.5)/(f/16) = 16/5.6 = 2.857
The diameter with f/5.6 is 2.857 fold larger than the opening with f/16, so is the radius.
The area of the two openings are pi*1^2 and pi*2.857^2 --> the area of the wider lens is
2.857^2 = 8.163 fold larger than the opening of the smaller opening.
The light coming through the lens in a certain time is proportional to the area. -->
There comes 8.163 more light through the large opening than through the small opening-->
The time must be 8.163 fold shorter than 1/60 second:
(1/60)/8.163 = 1/500 second.
1/500 s
4.
5.1600