Answer the following questions related to ex. 35.1 and effective focal length: (a) redo example 35.1, but this time with the two lenses separated by 10mm rather than 60mm. you should still assume that a 10-cm-tall object is 500 mm from the first lens. what is the effective focal length of this double-lens system? (b) prove the following statement: if the distance separating two lenses is zero, then the effective local length of the system is f, where 1 f = 1 f1 + 1 f2 to prove this, basically redo the same problem as part a, but don’t plug in numbers. 2. suppose you have a picture that is very underexposed (too dark). how would you improve the image under the following conditions? (a) you are allowed to change the focal length, but not the aperture size nor shutter speed. (b) you are allowed to change the aperture size, but not the focal length nor shutter speed. (c) you are allowed to change the shutter speed, but not the focal length nor aperture size. (d) what happens to the magnification of the picture in each of the three cases above?