Assertion (A): A solid glass sphere is placed in air. A light ray enters into the sphere from outside. The ray cannot undergo total internal reflection inside the sphere.
Reason (R): The angle of incidence at \(\text{1}^ \ext{st}\) surface cannot be greater than the critical angle for air-glass system.
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
A light ray can undergo Total Internal Reflection (TIR) inside a glass sphere if the conditions are met at the glass-air interface. The reason incorrectly relates the critical angle to the first surface incidence and does not explain why TIR could not occur. Both A and R are false.
Assertion (A): Wavelength of light changes on changing medium.
Reason (R): Light ray always deviates from its path when refracted.
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
When light enters a new medium, its speed and wavelength change, while frequency remains constant. Light deviates upon refraction unless it strikes normally. Both A and R are true, but R describes a characteristic of refraction, not the cause of wavelength change.
Assertion (A): Turpentine is denser medium than water for light.
Reason (R): Unit volume of turpentine is heavier than unit volume of water.
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
Turpentine has a higher refractive index (optically denser) than water, so A is true. However, turpentine's mass density is less than water's, meaning a unit volume of turpentine is lighter than water. Therefore, 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
View Answer
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
View Answer
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): The sun appears oval shape at sunrise.
Reason (R): At the time of sunrise sun appears a little before the actual sunrise.
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
Atmospheric refraction causes sunlight to bend as it passes through Earth's atmosphere. This phenomenon makes the sun appear to rise earlier and distorts its shape into an oval or flattened form at the horizon due to differential refraction. Both Assertion (A) and Reason (R) are true, and (R) provides a correct explanation for (A).
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
View Answer
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.