A ray of light falls on a prism \(ABC\) \((AB= BC)\) and travels as shown in figure. The refractive index of the prism material should be greater than:

                    

1. \(4 /{3}\) 2. \( \sqrt{2}\)
3. \(1.5\) 4. \( \sqrt{3}\)

Subtopic:  Prisms |
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Level 2: 60%+
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The focal length of a glass \((\mu = 1.5)\) lens in air is \(20~\text{cm}.\) If it is dipped in water \(\left(\mu= \frac{4}{3}\right)\) its focal length in water will be:
1. \(80~\text{cm}\) 2. \(40~\text{cm}\)
3. \(60~\text{cm}\) 4. \(20~\text{cm}\)
Subtopic:  Lens Makers' Formula |
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Level 2: 60%+
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When a concave mirror of focal length \(f\) is immersed in water, its focal length becomes \(f',\) then:
1. \(f' = f\)
2.  \(f'<f\)
3.  \(f'>f\)
4.  The information is insufficient to predict
Subtopic:  Reflection at Spherical Surface |
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Level 2: 60%+
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Two convex lenses of focal length \(X\) and \(Y\) are placed parallel to each other. An object at infinity from the first lens forms its image at infinity from the second lens. The separation between the two lenses should be:
1. \(X+Y\) 2. \(\dfrac{X +Y}{2}\)
3. \(X-Y\) 4. \(\dfrac{X -Y}{2}\)
Subtopic:  Lenses |
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Level 2: 60%+
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A plane mirror is placed at the bottom of a fish tank filled with water of refractive index \(\dfrac{4}{3}.\) The fish is at a height \(10~\text{cm}\) above the plane mirror. An observer \(O\) is vertically above the fish outside the water. The apparent distance between the fish and its image is:

1. \(15​​\text{cm}\) 2. \(30~\text{cm}\)
3. \(35~\text{cm}\) 4. \(45~\text{cm}\)
Subtopic:  Refraction at Plane Surface |
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Level 2: 60%+
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If \(C_1,~C_2 ~\mathrm{and}~C_3\) are the critical angle of glass-air interface for red, violet and yellow color, then:

1. \(C_3>C_2>C_1\) 2. \(C_1>C_2>C_3\)
3. \(C_1=C_2=C_3\) 4. \(C_1>C_3>C_2\)
Subtopic:  Total Internal Reflection |
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Level 2: 60%+
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An object is placed \(20~\text{cm}\) in front of a concave mirror of a radius of curvature \(10~\text{cm}.\) The position of the image from the pole of the mirror is:
1. \(7.67~\text{cm}\)
2. \(6.67~\text{cm}\)
3. \(8.67~\text{cm}\)
4. \(9.67~\text{cm}\)

Subtopic:  Reflection at Spherical Surface |
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Level 1: 80%+
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When a ray of light falls on a given plate at an angle of incidence \(60^{\circ}\), the reflected and refracted rays are found to be normal to each other. The refractive index of the material of the plate is:
1. \(\frac{\sqrt{3}}{2} \) 2. \(1.5 \)
3. \(1.732 \) 4. \( 2\)
Subtopic:  Refraction at Plane Surface |
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A thin rod of length \(\dfrac{f}{3}\) lies along the axis of a concave mirror of focal length \(f.\) One end of its magnified, real image touches an end of the rod. The length of the image is:

1. \(f\) 2. \(\dfrac{f}{2}\)
3. \(2f\) 4. \(\dfrac{f}{4}\)
Subtopic:  Reflection at Spherical Surface |
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Level 3: 35%-60%
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A thin equiconvex lens of power \(P\) is cut into three parts \(A,B,\) and \(C\) as shown in the figure. If \(P_1,P_2\) and \(P_3\) are powers of the three parts respectively, then:
            

1. \(P_1=P_2=P_3\) 2. \(P_1>P_2=P_3\)
3. \(P_1<P_2=P_3\) 4. \(P_2=P_3=2P_1\)
Subtopic:  Lenses |
 73%
Level 2: 60%+
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