Assertion (A): In telescopes objective lens is taken of large diameter or aperture.
Reason (R): Larger aperture remove spherical aberration.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
A large diameter objective lens in telescopes increases the light-gathering power and improves resolving power, allowing observation of fainter and finer details. Hence, Assertion (A) is true. However, spherical aberration generally *increases* with larger apertures, as rays further from the principal axis are not focused at the same point. Thus, Reason (R) is false.
Assertion (A): In case of single refraction by plane surface image and object are on the same side.
Reason (R): If object is real, image will be virtual and vice-versa.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
For a plane refracting surface, a real object always forms a virtual image. This virtual image is formed on the same side of the plane surface as the object itself, as light rays appear to diverge from it after refraction.
Assertion (A): In displacement method of finding focal length of a convex lens, if magnification in a position of lens is \( -2 \), then magnification in another position of lens should be \( -1/2 \).
Reason (R): This method can not be applied for diverging lens.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
In the displacement method, if magnifications are \( m_1 \) and \( m_2 \) for two positions, then \( m_1 m_2 = 1 \). If \( m_1 = -2 \), then \( m_2 = -1/2 \). The method requires formation of real images, which diverging lenses cannot produce for real objects.
Assertion (A): If one half of a mirror is covered by an opaque material, then only half image of the object is formed.
Reason (R): By covering one half of the mirror, focal length of mirror will be halved.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Covering half a mirror reduces the intensity of the image but a complete image is still formed. The focal length of a mirror depends only on its radius of curvature, not on the aperture or how much of its surface is exposed.
Assertion (A): In medical technology endoscopy, optical fibres are used to facilitate visual examination of internal organs of the body.
Reason (R): Optical fibres are fabricated so that there should be very less absorption of light and hence no appreciable loss of light intensity.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Optical fibers are indeed used in endoscopy to transmit light for internal examination. This is possible because they are designed for very low light absorption, ensuring minimal loss of light intensity over their length. Both statements are true and R explains A.
Assertion (A): When light passes through a prism, it disperses while if the same light passes through a rectangular glass slab of same material, it doesn’t disperse.
Reason (R): Dispersive power of prism is non zero while that of glass slab is zero.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
A prism disperses light because its non-parallel surfaces separate colors due to varying refractive indices. A rectangular slab also disperses light internally, but the emergent rays are parallel, resulting in no net angular dispersion. Dispersive power is a material property and is non-zero for any dispersive medium, including glass slabs.
Assertion (A): In a magnifying glass, the angle subtended by an object at the eye is equal to the angle subtended by its virtual image at the eye. Still the magnifying glass provides angular magnification.
Reason (R): Magnifying glass produce a virtual magnified image of the object.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is false. Angular magnification occurs precisely because the virtual image subtends a larger angle at the eye than the object alone. Reason (R) is true; a magnifying glass (convex lens) forms a virtual, upright, and magnified image.
Assertion (A): Concave mirror can’t form virtual image of a virtual object.
Reason (R): Convex mirror can’t form real image of a real object.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Both Assertion (A) and Reason (R) are false. A concave mirror can form a virtual image of a virtual object if the object is between its pole and focus. A convex mirror can form a real image of a virtual object, for example, if the virtual object is placed between its pole and focus.
Assertion (A): When white light passes successively through two identical prisms, one inverted with respect to other, then in emergent side, again white light is obtained.
Reason (R): Prism has no ability to create colour but it only separates the colours already present in white light.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; the second inverted prism recombines the dispersed light back into white light. Reason (R) is true; prisms only disperse existing colours, they do not create new ones. Reason (R) correctly explains Assertion (A).
Assertion (A): Secondary rainbow is fainter than primary rainbow.
Reason (R): Secondary rainbow is seen due to the scattering of primary rainbow through water molecules.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
Assertion (A) is true; secondary rainbows are fainter due to two internal reflections causing more light loss. Reason (R) is false; secondary rainbows result from light undergoing two internal reflections in raindrops, not scattering of a primary rainbow.