3) (20 pts.) Compute the focal length of a biconcave thin lens immersed in water. The lens is made of flint glass, with index of refraction 1.66. The radii of the surfaces of the lens are 10 cm for the left surface and 20 cm for the right surface (both given in magnitude). The index of water is 1.33.

22 The focal length of a simple magnifier is 8.00 cm. Assume the magnifier is a thin lens placed very close to the eye. (a) How far in front of the magnifier should an object be placed if the image is formed at the observer's near point, 25.0 cm in front of her eye? (b) If the object is 1.00 mm high, what is the height of its image formed by the magnifier?

Ch 26, problem 7 An object is 21.0 cm from a converging lens, and the image falls on a screen. When the object is moved 3.50 cm closer to the lens, the screen must be moved 2.20 cm farther away from the lens to register a sharp image. Determine the focal length of the lens.

7) Both lenses of a compound microscope have focal lengths of 1 cm. The barrel length is 26.95 cm. Deteimine the total magnification for an object placed 1.04 cn below the objective,