Assertion (A): An object placed at a distance less than \(25 \text{ cm}\), in front of a normal eye. The image of this object on retina is blurred.
Reason (R): Image is formed before retina.
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
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The near point for a normal eye is \(25 \text{ cm}\), meaning objects closer than this cannot be focused clearly on the retina. So, Assertion (A) is true. However, for a normal eye attempting to focus on an object closer than its near point, the image would effectively form *behind* the retina if the lens power is insufficient, not before it. Thus, Reason (R) is false.
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
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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): Splitting of light into its component colours is possible in refraction at plane surface of two media.
Reason (R): On each refraction dispersion is possible but in prism at both surface dispersion is in same direction so it is clearly seen.
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
Dispersion, the splitting of light into its constituent colors, occurs during refraction because the refractive index of a medium depends on the wavelength of light. This effect is present at any plane refractive surface. In a prism, the refractions at both surfaces cause deviations for different colors that add up in the same direction, making the overall dispersion more noticeable. Both A and R are true, and R explains A.
Assertion (A): In case of a concave mirror if a point object is moving towards the mirror along its principal axis then its image will always move away from the mirror.
Reason (R): In case of reflection (along the principal axis of mirror) object and image always travel in same directions.
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
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For a concave mirror, if an object moves from infinity towards the center of curvature (C), its real image moves from the focus (F) to C, thus moving *towards* the mirror. So, Assertion (A) is false. Also, the object and image do not *always* travel in the same direction along the principal axis; their relative motions depend on the object's position relative to F and C. Hence, Reason (R) is also false. Both A and R are false.
Assertion (A): Any ray of light suffers a deviation of \(180° – 2i\) after one reflection from plane mirror.
Reason (R): For normal incidence of light on the plane mirror deviation 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
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For a plane mirror, the angle of deviation \(delta\) for an incident ray is given by \(delta = 180° - 2i\), where \(i\) is the angle of incidence. Thus, Assertion (A) is true. For normal incidence, \(i=0\), and the ray retraces its path, meaning its direction is reversed. This corresponds to a deviation of \(180°\), not zero. Hence, Reason (R) is false.
Assertion (A): Rear view mirror of a vehicle is a convex mirror.
Reason (R): It never makes real image of real objects.
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
Convex mirrors are used as rear-view mirrors because they provide a wider field of view and always form virtual, erect, and diminished images of real objects. This property is crucial for drivers to see a larger area behind the vehicle and perceive objects as being further away. Both A and R are true, and R correctly explains the suitability of convex mirrors for this application.
Assertion (A): There is refracting glass slab between Ram and Anoop, then Ram appears nearer to Anoop as Compared to the actual distance between them.
Reason (R): Ray of light starting from Ram will undergo two times refraction before reaching to Anoop.
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
When light rays pass from a denser medium (glass slab) to a rarer medium (air), they bend away from the normal, making the object appear closer than its actual position. This phenomenon is known as apparent depth.
Light from Ram travels through the slab, undergoing refraction at both surfaces (air to glass and glass to air), leading to this apparent shift. Both A and R 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 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.