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11. Which are not complementary colours?
A. Red and cyan
B. Red and magenta
C. Green and yellow
D. Green and magenta
ANSWER:B
SOLUTION :Red and magenta** are not complementary colors.
12. When a light wave is reflected from a mirror, there is a change in its ________.
A. Frequency
B. Amplitude
C. Wavelength
D. Velocity
ANSWER:B
SOLUTION:The focal length of a normal human eye lens is about 2 cm or 20 mm when the eye is relaxed. Focal length is the distance between the eye lens and the retina, which acts as a screen on which the real image is formed.
13. Which colour is the complementary colour of yellow?
A. Blue
B. Green
C. Orange
D. Red
ANSWER:A
SOLUTION:Bright yellow is also commanding next to blue, which is its complementary color on the color wheel.
14. Televisions signals cannot be received beyond a certain distance because________.
A. Signals are weak
B. Antenna is weak
C. Air absorbs signals
D. The surface of the earth is curved
ANSWER:D
SOLUTION:The signal transmitted from a TV tower cannot be received beyond a certain distance because the surface of the Earth is curved. Signal waves transmitted from a transmitter get absorbed or blocked by the curvature of Earth and are not received.
15. In which year did Ole Roemer measure the speed of light for the first time in history?
A. 1776
B. 1676
C. 1876
D. 1867
ANSWER:B
SOLUTION:In 1676, the Danish astronomer Ole Roemer (1644–1710) became the first person to measure the speed of light. Roemer measured the speed of light by timing eclipses of Jupiter’s moon Io.
16. The minimum height of mirror , required to see whole stand up image of a man of height 1.50 meter shall be ________.
A. 0.75 metre
B. 1.00 metre
C. 1.50 metre
D. 3.00 metre
ANSWER:A
SOLUTION :Light enters the eye through a thin, transparent, dome-shaped membrane called the cornea. The cornea is the clear front layer of the eye that bends light to help the eye focus.
17. Image formed by the actual intersection of reflecting rays ( which we see on the screen ) _____.
A. Virtual
B. Imaginary
C. Probable
D. Real
ANSWER:D
SOLUTION:A real image is formed when reflecting rays actually intersect, rather than appearing to meet at a point. A real image can be obtained on a screen.
18. Which of the following is used to take 3 – dimensional pictures?
A. Photography
B. Holography
C. Radiography
D. None of these
ANSWER:B
SOLUTION: Holography
Uses an interference pattern to encode a light field, which diffracts light into a reproduction of the original light field when lit. This creates a 3D image without the need for special glasses or objects. The result of holography is called a hologram.
19. Which of the following types of the mirror is used to see the traffic behind the car ?
A. Convex mirror
B. Concave mirror
C. Plane mirror
D. Spherical mirror
ANSWER:A
SOLUTION: In motor vehicles, a convex mirror is attached near the driver’s seat to give him the view of the traffic behind.
20. A spoon which looks bent in water is an example of which of the following ?
A. Reflection
B. Refraction
C. Retention
D. Focus
ANSWER:B
SOLUTION: The spoon appears bent in a glass of water due to refraction, the change in direction of light waves as they pass from one medium into another.