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21. The centre of the reflecting surface of a sperical mirror is called the _______.
A. Pole
B. Radius
C. Centre of curvature
D. Focus
ANSWER:A
SOLUTION :The centre of the reflecting surface of a spherical mirror is known as the pole.
22. When light waves pass from air to glass the variable affected are ________.
A. Wavelength, frequency and velocity
B. Velocity and frequency
C. Wavelength and frequency
D. Wavelength and Velocity
ANSWER:D
SOLUTION:When a light ray enters from rarer to denser (air to glass) medium wavelength and velocity will get affected. As the ray bends in passing through different media which results in a decrease in wavelength. The velocity also decreases.
23. Which of the following statement is true ?
A. The light has a greater velocity
B. The sound has the greatest velocity
C. Celestial objects have the greatest velocity
D. Rocket has the greatest velocity
ANSWER:A
SOLUTION:The light has a greater velocity.
24. What will be the size of image formed by a concave mirror when an object placed between pole and focus ?
A. Same size
B. Enlarged
C. Point size
D. Diminished
ANSWER:B
SOLUTION:A highly enlarged image is formed at infinity if the object is at the focus of a concave mirror.
25. The magnifying glass is ________.
A. Convex lens
B. Convex mirror
C. Concave lens
D. Concave mirror
ANSWER:A
SOLUTION:A magnifying glass is a convex lens, used to make objects appear larger than they actually are. While using a magnifying glass, the distance between object and glass is kept shorter than the focal length of the lens.
26. For normal eyes what is the minimum distance for clear vision?
A. 10 cm
B. 15 cm
C. 20 cm
D. 25 cm
ANSWER:D
SOLUTION :The minimum distance for a clear vision of a normal human eye is 25 cm. It is also known as the least distance of distinct vision or near the point of an eye. The human eye is a specialized sense organ that is capable of receiving visual images and then carried to the brain.
27. The correct relation between the radius of curvature R and focal length f of a spherical mirror is ______.
A. R = f
B. R = 2f
C. R = 3f
D. R = 4f
ANSWER:B
SOLUTION:The corret relation between the radius of curvature (R) and the focal length(f) is given by, R=2f.
28. Rainbow is seen after rain because of hanging molecules of water which act as __________.
A. Lenses
B. Prism
C. Mirrors
D. Mirrors
ANSWER:B
SOLUTION: Since the prism also splits the white light into its constituent colors. Similarly, water droplets suspended in the air also acts as a prism for the light falling on their surfaces. Hence, we see a rainbow in the sky after the rainfall.
29. What is the distance between the focal point or focus point in the lens and the vision center or optical center?
A. Radius of curvature
B. Principal line
C. Focal length
D. Focus
ANSWER:C
SOLUTION: The distance between the optical center of a lens and its focal point is called the focal length. It’s an important measurement in determining the magnifying power and image formation of a lens or mirror. The symbol, f, represents the focal length.
30. In a concave mirror when the object is placed at infinity which of the following applies to the image ?
A. Real, inverted image of the same size at centre of curvature
B. Real, inverted, highly diminished image at focus
C. Real, inverted highly enlarged image at centre of curvature
D. Real, inverted, diminished image between centre of curvature (c) and principal focus (F)
ANSWER:B
SOLUTION: Whenever the object is placed at infinity in a concave mirror it produces a real, inverted and highly diminished image at the focus.