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41. Which one of the following statements regarding lenses is not correct ?
A. A convex lens produces both real and virtual images
B. A concave lens produces both real and virtual images
C. A convex lens can produce images equal, greater and smaller than the size of the object
D. A concave lens always produces images smaller than the size of the object
ANSWER:B
SOLUTION :A concave lens produces both real and virtual images is not correct regarding lenses. Explanation: Convex lenses can form either real or virtual images.
42. Lenses with two focal lengths are used by persons suffering from _________.
A. Myopia and hypermetropia
B. Myopia or hypermetropia
C. Myopia but not hypermetropia
D. Hypermetropia but not myopia
ANSWER:A
SOLUTION:Bifocal lenses, which have two focal lengths, are used by people suffering from both myopia (nearsightedness) and hypermetropia (farsightedness). The upper part of a bifocal lens is concave to correct distant vision, while the lower part is convex to correct near vision.
43. Which combination of colour is the most convenient during day and night time ?
A. Orange and blue
B. White and black
C. Yellow and blue
D. Red and green
ANSWER:D
SOLUTION:Some say that red and green is the most convenient color combination for both day and night because of its precise visibility. Red, green, and blue are the primary colors in the RGB color model.
44. The Quantum Theory of light was given by _______.
A. Einstein
B. Planck
C. Newton
D. Faraday
ANSWER:B
SOLUTION:Quantum Theory was propounded by physicist Max Planck in 1900 when he made an assumption that the energy was made of ‘quanta’ or individual units.
45. The phenomenon of deviation of light rays from their original path, when they pass from one medium to another, is called ________.
A. Reflection
B. Refraction
C. Obstruction
D. Diffraction
ANSWER:B
SOLUTION:Refraction is a phenomenon in which when a ray passes from one medium to another it bends away from its straight-line path due to the difference in optical densities or refractive indices of the two mediums. This bending is known as deviation.
46. If the Focal length of a mirror is +15, It is _________.
A. Plane mirror
B. Concave mirror
C. Convex mirror
D. Double lens
ANSWER:C
SOLUTION : If a mirror has a focal length of +15 cm, then it is a convex mirror. The focal length of a mirror is the distance between the mirror’s center and its focal point. A positive focal length indicates that a mirror converges light, while a negative focal length indicates that it diverges light.
47. Which one of the following lenses should be used to correct the defect of astigmatism?
A. Cylindrical lens
B. Concave lens
C. Convex lens
D. Bifocal lens
ANSWER:A
SOLUTION:Cylindrical lenses are used to correct astigmatism, an eye defect that occurs when the cornea or lens of the eye has an irregular curvature. This causes light to bend unevenly, resulting in blurry or distorted vision.
48. The ratio of the speed of light in a medium to a vacuum is called________.
A. Reflective index
B. Refractive index
C. Medivec Index
D. Air Quality Index
ANSWER:B
SOLUTION: The ratio of the speed of light in a vacuum to the speed of light in a medium is called the refractive index. It’s also known as the absolute refractive index.
49. Which one of the colours has the longest wavelength?
A. Green
B. Yellow
C. Blue
D. Red
ANSWER:D
SOLUTION: Red has the longest wavelength in the visible spectrum, ranging from 625 to 740 nanometers. Violet has the shortest wavelength, around 380 nanometers.
50. An air bubble in water will act like a _______.
A. Convex mirror
B. Convex lens
C. Concave mirror
D. Concave lens
ANSWER:D
SOLUTION: Refractive index of water is greater than that of air which makes the focal length of the air bubble to be negative. Thus an air bubble acts as concave lens in water.