← All Chapters

Ray Optics

Practice Questions:

Question 1: easy

Assertion (A): A simple microscope may have different magnification for different persons.

Reason (R): All persons must have the same near point distance of \(25\text{ cm}\).

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

Assertion (A) is true as magnification depends on individual near point, which varies. Reason (R) is false as the near point varies for different individuals and is not universally \(25\text{ cm}\).

💬 Discuss this Question

Question 2: easy

Assertion (A): If an object placed on the optic axis of a lens is illuminated by white light, then image formed will be coloured and not exactly white.

Reason (R): The lens has different focal lengths for different colours.

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

Assertion (A) is true due to chromatic aberration. Reason (R) is true and correctly explains (A) because the refractive index of lens material varies with wavelength, causing different focal lengths for different colors.

💬 Discuss this Question

Question 3: easy

Assertion (A): Paraxial rays are always parallel to the principal axis.

Reason (R): A parallel beam parallel to principal axis converges at the focal point.

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

Assertion (A) is false; paraxial rays are simply close to the axis, not necessarily parallel. Reason (R) is also false because due to spherical aberration, a real parallel beam does not perfectly converge to a single focal point.

💬 Discuss this Question

Question 4: easy

Assertion (A): The image focus (\(2^{\text{nd}}\) focus) and the object focus (\(1^{\text{st}}\) focus) are on the opposite side of the biconvex or biconcave lens.

Reason (R): The radii of curvature of a biconvex lens and biconcave lens are on the opposite side of the 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

Assertion (A) is true; the two principal focal points are on opposite sides of the lens. Reason (R) is true, describing the geometric arrangement of the centers of curvature. However, (R) does not explain (A).

💬 Discuss this Question

Question 5: easy

Assertion (A): Keeping a point object fixed, if a plane mirror is moved, the image will also move.

Reason (R): In case of a plane mirror, distance of object and its image is equal from any point on the mirror.

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

Assertion (A) is true; the image position is relative to the mirror, so it moves with the mirror. Reason (R) is true as per the property of plane mirrors, where \(OP = IP\). (R) correctly explains (A) as image movement maintains this property.

💬 Discuss this Question

Question 6: easy

Assertion (A): A lens has two principal focal lengths which may be different in magnitude.

Reason (R): The distance of both principal focus from optical centre of lens depend on the two radii of curvature of the lens. Distance of both principal focus from optical centre a lens are same only if radii of curvature of both sides of lens are same.

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

Assertion (A) is true if the lens is in different media on either side. Reason (R) is false because for a thin lens in the same medium, magnitudes of focal lengths are always equal, irrespective of the equality of radii of curvature.

💬 Discuss this Question

Question 7: easy

Assertion (A): If there is relative motion between a point object & a plane mirror then there must be relative motion between object and image formed by mirror.

Reason (R): If the gap between object and mirror will change, the gap between object and image remains same.

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

Assertion A is true because if the object moves relative to the mirror, its image also moves, causing relative motion between object and image. Reason R is false because for a plane mirror, the object-image gap is twice the object-mirror gap, so if the object-mirror gap changes, the object-image gap also changes.

💬 Discuss this Question

Question 8: easy

Assertion (A): When the upper half of a converging lens is missing, a real image formed by the lens for a real object will lack its lower half.

Reason (R): The real image formed by a thin lens for a real object will be always erected.

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

Assertion A is false because even with half the lens missing, a complete image is formed, but its intensity is reduced. Reason R is false as real images formed by a thin lens for a real object are generally inverted, not always erected.

💬 Discuss this Question

Question 9: easy

Assertion (A): A parallel beam of light travelling in air can be displaced laterally by a parallel transparent slab by distance more than the thickness of the plate.

Reason (R): The lateral displacement of light travelling in air increases with fall in value of refractive index of slab.

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

Assertion A is false as the lateral displacement of light through a parallel slab is always less than or equal to its thickness. Reason R is false because lateral displacement decreases as the refractive index of the slab falls.

💬 Discuss this Question

Question 10: easy

Assertion (A): A virtual image formed by plane mirror may be inverted.

Reason (R): Longitudinal magnification in this case of plane mirror is \(-1\).

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

Assertion A is true because a plane mirror forms a laterally inverted image. Reason R is true because for a plane mirror, longitudinal magnification \(m_L = - (v/u)^2 = -1\). However, longitudinal magnification does not explain lateral inversion.

💬 Discuss this Question

1 2 3 … 10 Next »