How far from a lens of focal length 50. 0 mm must the object the placed if it is

Question

How far from a lens of focal length 50. 0 mm must the object the placed if it is to form a virtual image magnified in size by a factor of three? A) 54. 4 mm B) 38. 3 mm C) 42. 2 mm D) 48. 0 mm E. 33. 3 mm 24) John's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and erect, what is the focal length of the mirror? A) 50 cm B) 10 cm C) 40 cm D) 20 cm E) 30 cm 25) A object is 15 cm in front of a concave mirror, and the image is 5. 0 cm in front of the mirror. What is the focal length of the mirror? A) 1. 6 cm B) 7. 5 cm C) 3. 8 cm D) 0. 25 cm E) 20 cm 26) Light of wavelength lambda = 500 nm passes through a pair of slits with separation 2. 6 times 10^-5 m. What is the angle corresponding to the second bright fringe? A) 2. 2degree B) 3. 7degree C) 4. 3degree D)1. 5degree E) 5. 0degree 27) The near point of a farsighted person is 100 cm. She places reading glasses close to her eye, and with them she can comfortably read a newspaper at a distance of 25 cm. What lens power is required? A) -2. 5 D B) -2. 0 D c) +3. 0D D) +3. 2D E) +2. 5D 28) An object is 14 cm in front of a convex mirror. The image is 5. 8 cm behind the mirror. What is the focal length of the mirror? A) 0-9. 9 cm B) -4. 1 cm C) -8. 2 cm D) -20cm 29) Suppose you place your face in front of a concave mirror.

Explanation / Answer

(26) Using the equation for the double sli interference:

sin  = n* / d

   => sin  = 2*(500*10^-9) / (2.6*10^-5) = (1/26)

=>     = sin^-1(1/26) = 2.2° ...............Option_(A) ...........Correct

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