(3) Which of the statements are correct (indicate with a C) and which are incorr

Question

(3) Which of the statements are correct (indicate with a C) and which are incorrect (indicate with an D? a) To correct for far sightedness a diverging (concave) lens is used to put the image of an object located at 25 em at the near point. b) An object placed at the focal point of a convex mirror will not produce an image. c) A block of unknown index of refraction is submerged in Jello with index n = 1.4. A light ray in the block is incident on the block-Jello surface and bounces as shown. From this we know the block must have an index of refraction greater than Jello. 5050 refractive power of glasses with a focal length of 43 cm is approximately 2.4 diopters. e) A source of unpolarized light is located at point A. If the intensity of light at point C is 1/4 that of the light at point A, the axes of polarization of the polarizers are at 45 with respect to cach other (4) The network shown is assembled with uncharged capacitors with CX-2 CY-3F and Cz-1 and open switches, s and S2. A potential difference Vab = +120V is applied between points a and b. After the circuit is assembled switch S2 is closed then Si is closed. The total energy stored in this circuit is: a S1 Vab+120V S2 a) 0.022 J b) 0.053 J 0.011J d) 0.026J 0.005

Explanation / Answer

Ans 3

Part(a)

Far sightedness is corrected by using convex lens. So this statement is incorrect(I).

Part(b)

If an object is placed at the focal point of a concave mirror, the image will be at infinity.

So the statement is incorrect(I).

Part C

For total internal reflection, two conditions are necessary;(1) refractive index of the incident medium must

be larger than the refracting medium and (2) angle of incidence must exceed critical angle.

Hence, the statement here is correct(C).

Ans(d)

43cm=0.43 m

Refractive power P = 1/ focal length(in m) = 2.33 D

So the answer is approximately correct(C)

Ans (e)

When unpolarized light of intensity I passes through the first polarizer, it polarizers the beam with intensity I/2.

The next polarizer(called analyser) reduces the intensity by a factor of cos2 heta according to Malus law.

As the final intensity is 1/4 of the original intensity, hence, cos2 hate=1/2 i.e angle heta=45 0.

So this answer is correct(c)

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