Q1. In a concave lens, the focal length is: (2023)
Solution:
The focal length of a concave lens is negative, indicating that it diverges light rays.
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Q2. In a ray diagram for a concave lens, the rays parallel to the principal axis appear to diverge from which point? (2021)
Solution:
In a ray diagram for a concave lens, rays parallel to the principal axis appear to diverge from the focal point.
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Q3. Which of the following statements is true for a concave lens? (2019)
Solution:
A concave lens diverges light rays, and it has a negative focal length.
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Q4. What type of lens is used to correct hypermetropia? (2021)
Solution:
A convex lens is used to correct hypermetropia (farsightedness) as it converges light rays before they enter the eye.
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Q5. What is the focal length of a concave mirror if the object is placed at a distance of 30 cm and the image is formed at a distance of 15 cm from the mirror? (2021)
Solution:
Using the mirror formula, 1/f = 1/v + 1/u. Here, v = -15 cm (image distance is negative for concave mirror) and u = -30 cm. Therefore, 1/f = 1/(-15) + 1/(-30) = -1/10. Thus, f = 10 cm.
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Q6. A light ray strikes a plane mirror at an angle of 30 degrees to the normal. What is the angle of reflection? (2023)
Solution:
According to the law of reflection, the angle of reflection is equal to the angle of incidence. Therefore, the angle of reflection is also 30 degrees.
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Q7. Which of the following is a characteristic of the image formed by a concave mirror when the object is placed between the focal point and the mirror? (2019)
Solution:
When the object is placed between the focal point and the mirror, the image formed by a concave mirror is virtual and erect.
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Q8. What happens to the speed of light as it passes from air into water? (2022)
Solution:
The speed of light decreases when it passes from a less dense medium (air) to a denser medium (water).
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Q9. In which case does total internal reflection occur? (2022)
Solution:
Total internal reflection occurs when light travels from a denser medium to a rarer medium at an angle greater than the critical angle.
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Q10. In a concave lens, the focal length is always: (2020)
Solution:
The focal length of a concave lens is always negative, as it diverges light rays.
