## RAY OPTICS AND OPTICAL INSTRUMENTS-15 Quiz

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.</.

Q1. A parallel beam of light falls axially on a thin converging lens of focal length 20 cm. The emergent light falls or a screen placed 30 cm beyond the lens. An opaque plate with a triangular aperture, side 1 cm, is in contact with the lens. (see figure)Which one of the following diagrams best shows to appearance of the patch of light seen on the screen?
•
•
•
•
Solution
The image on the screen is real and inverted
The size of the image on the screen has aperture size given by
Size =1.0 (10/20)=0.5 cm Hence, the path of light on the screen is best represented by diagram (d)

Q2.A light ray travelling in glass medium is incident on glass-air interface at an angle of incidenceÎ¸. The reflected (R) and transmitted (T) intensities, both as function of Î¸, are plotted. The correct sketch is
•
•
•
•
Solution

After critical angle reflection will be 100% and transmission is 0 %. Options (b) and (c) satisfy this condition.
But option (c) is the correct option.
Because in option (b) transmission is given 100% at Î¸ = 0°, which is not true ∴ Correct answer is (c).
Q3.  A concave mirror is placed on a horizontal table with its axis directed vertically upward. Let O be the pole of the mirror and C its center of curvature. A point object is placed at C. It has a real image, also located at C. If the mirror is now filled with water, the image will be
•   Real and will remain at C
•  Real and located at a point between C and ∞
•  Real and located at a point between O and C
•  Real and located at a point between C and O
Solution

Q4. Two identical glass (Î¼_g=3/2) equiconvex lenses of focal length f are kept in contact. The space between the two lenses is filled with water (Î¼_w=4/3). The focal length of the combination is
•  66° CW
•  66° ACW
•  54° ACW
•  54° CW
Solution

Q5. A glass sphere of radius R=10 cm is kept inside water. A point object O is placed at 20 cm from A as shown in figure. Find the position and nature of the image when seen from other side of the sphere. Given Î¼_g=3/2 and Î¼_w=4/3
•  200 cm, virtual
•  100 cm, real
•  100 cm, virtual
•  300 cm, virtual
Solution
Q6. A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a
•  Convergent lens of focal length 3.5 R
•  Convergent lens of focal length 3.0 R
• Divergent lens of focal length 3.5 R
•  Divergent lens of focal length 3.0
Solution
f_l/f_a =( _a Î¼_g-1)/( _l Î¼_g-1)=(1.5-1)/(1.5/1.75-1)=-(1.75×0.50)/0.25=-3.5
∴f_l=-3.5 f_a⇒f_l=+3.5R [∵f_a=R]
Hence on immersing the lens in the liquid,
it behaves as a converging lens of focal length 3.5 R

Q7. A point source of light is placed in front of a plane mirror as shown in figure Determine the length of reflected path of light on the screen ∑
•  L
•  2L
•  3L/2
•  L/2
Solution

Q8.The critical angle for light going from medium X into medium Y is Î¸. The speed of light in medium X is v. The speed of light in medium Y is
•  b) vcos⁡Î¸
•  v/cos⁡Î¸
•  v sin⁡Î¸
•  v/sin⁡Î¸°
Solution

Q9. A given ray of light suffers minimum deviation in an equilateral prism P? Additional prisms Q and R of identical shape and of the same material as P are now added as shown in figure. The ray will suffer:
•  Greater deviation
•  No deviation
•  Same deviation as before
•  Total internal reflection
Solution

Q10. A ball is dropped from a height of 20m above the surface of water in a lake. The refractive index of water is4/3. A fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is 12.8 m above the water surface, the fish sees the speed of ball as
•  9 ms^(-1)
•  12ms^(-1)
•  16 ms^(-1)
• 21.33 ms^(-1)
Solution

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