1
KCET 2021
MCQ (Single Correct Answer)
+1
-0

Two thin biconvex lenses have focal lengths $$f_1$$ and $$f_2$$. A third thin biconcave lens has focal length of $$f_3$$. If the two biconvex lenses are in contact, then the total power of the lenses is $$P_1$$. If the first convex lens is in contact with the third lens, then the total power is $$P_2$$. If the second lens is in contact with the third lens, the total power is $$P_3$$, then

A
$$P_1=\frac{f_1 f_2}{f_1-f_2}, P_2=\frac{f_1 f_3}{f_3-f_1}$$ and $$P_3=\frac{f_2 f_3}{f_3-f_2}$$
B
$$P_1=\frac{f_1-f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_3+f_1}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
C
$$P_1=\frac{f_1-f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_1 f_3}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
D
$$P_1=\frac{f_1+f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_1 f_3}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
2
KCET 2021
MCQ (Single Correct Answer)
+1
-0

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length $$30 \mathrm{~cm}$$ is $$2 \mathrm{~cm}$$. If a concave lens of focal length $$20 \mathrm{~cm}$$ is placed between the convex lens and the image at a distance of $$26 \mathrm{~cm}$$ from the lens, the new size of the image is

A
1.25 cm
B
2.5 cm
C
1.05 cm
D
2 cm
3
KCET 2021
MCQ (Single Correct Answer)
+1
-0

A slit of width $$a$$ is illuminated by red light of wavelength $$6500 \mathop A\limits^o$$. If the first diffraction minimum falls at $$30^{\circ}$$, then the value of $$a$$ is

A
$$6.5 \times 10^{-4} \mathrm{~mm}$$
B
1.3 micron
C
$$3250 \mathop A\limits^o$$
D
$$26 \times 10^{-4} \mathrm{~cm}$$
4
KCET 2021
MCQ (Single Correct Answer)
+1
-0

Which of the following statements are correct with reference to single slit diffraction pattern?

(I) Fringes are of unequal width.

(II) Fringes are of equal width.

(III) Light energy is conserved.

(IV) Intensities of all bright fringes are equal.

A
Both (I) and (III)
B
Both (I) and (IV)
C
Both (II) and (IV)
D
Both (II) and (III)
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