Ray Optics
Q. A beam of light passes through a prism with an angle of 60 degrees and has a refractive index of 1.5. What is the angle of minimum deviation?
A.
30 degrees
B.
45 degrees
C.
60 degrees
D.
15 degrees
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Solution
For a prism, the angle of minimum deviation (D) can be approximated as D = A for small angles, thus D = 60 degrees.
Correct Answer: A — 30 degrees
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Q. A beam of light passes through a thin convex lens with a focal length of 15 cm. If the object is placed 30 cm from the lens, what is the image distance?
A.
10 cm
B.
15 cm
C.
20 cm
D.
30 cm
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Solution
Using the lens formula, 1/f = 1/v - 1/u; here, f = 15 cm and u = -30 cm. Thus, 1/v = 1/15 + 1/30 = 1/10, giving v = 10 cm.
Correct Answer: C — 20 cm
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Q. A concave lens has a focal length of -20 cm. What is the nature of the image formed when an object is placed at 30 cm from the lens?
A.
Real and inverted
B.
Virtual and erect
C.
Real and erect
D.
Virtual and inverted
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Solution
For a concave lens, the image formed is virtual and erect when the object is placed at any distance.
Correct Answer: B — Virtual and erect
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Q. A concave mirror has a focal length of 10 cm. An object is placed 30 cm in front of the mirror. Where will the image be formed?
A.
10 cm
B.
15 cm
C.
20 cm
D.
30 cm
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Solution
Using the mirror formula, 1/f = 1/v + 1/u, where f = -10 cm (concave mirror), u = -30 cm. Solving gives v = -15 cm, which means the image is formed 15 cm in front of the mirror.
Correct Answer: C — 20 cm
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Q. A concave mirror produces a virtual image of an object placed 10 cm in front of it. If the focal length of the mirror is 5 cm, what is the distance of the image from the mirror?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
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Solution
Using the mirror formula, 1/f = 1/v + 1/u. Here, f = -5 cm (concave mirror), u = -10 cm. Solving gives v = -10 cm.
Correct Answer: B — 10 cm
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Q. A lens has a focal length of +20 cm. What type of lens is it?
A.
Concave lens
B.
Convex lens
C.
Bifocal lens
D.
Cylindrical lens
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Solution
A positive focal length indicates that the lens is a convex lens, which converges light rays.
Correct Answer: B — Convex lens
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Q. A lens has a power of +2 diopters. What is its focal length?
A.
0.5 m
B.
1 m
C.
2 m
D.
3 m
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Solution
Power (P) is given by P = 1/f (in meters). Thus, f = 1/P = 1/2 = 0.5 m.
Correct Answer: B — 1 m
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Q. A light ray enters a glass prism with a refractive index of 1.5. If the angle of incidence is 30 degrees, what is the angle of refraction?
A.
15 degrees
B.
20 degrees
C.
25 degrees
D.
30 degrees
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Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). Here, n1 = 1 (air), n2 = 1.5, i = 30 degrees. Solving gives r = 19.2 degrees.
Correct Answer: B — 20 degrees
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Q. A light ray passes from air into glass with a refractive index of 1.5. If the angle of incidence is 30 degrees, what is the angle of refraction?
A.
18.4 degrees
B.
20 degrees
C.
22 degrees
D.
25 degrees
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Solution
Using Snell's law, n1 * sin(theta1) = n2 * sin(theta2). Here, n1 = 1 (air), n2 = 1.5 (glass), and theta1 = 30 degrees. Thus, sin(theta2) = (1 * sin(30))/1.5 = 0.333, giving theta2 ≈ 19.1 degrees.
Correct Answer: A — 18.4 degrees
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Q. A light ray passes through the center of curvature of a concave mirror. What will be the angle of reflection?
A.
0 degrees
B.
30 degrees
C.
45 degrees
D.
90 degrees
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Solution
When a light ray passes through the center of curvature, it strikes the mirror perpendicularly, resulting in an angle of reflection of 0 degrees.
Correct Answer: A — 0 degrees
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Q. A light ray strikes a glass slab at an angle of incidence of 45 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?
A.
30 degrees
B.
45 degrees
C.
60 degrees
D.
90 degrees
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Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). Here, sin(r) = (1 * sin(45)) / 1.5 = 0.471, giving r ≈ 28 degrees.
Correct Answer: A — 30 degrees
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Q. A light ray strikes a glass surface at an angle of 60 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?
A.
30 degrees
B.
40 degrees
C.
60 degrees
D.
90 degrees
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Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). Here, n1 = 1 (air), n2 = 1.5 (glass), i = 60 degrees. Solving gives r = 40 degrees.
Correct Answer: B — 40 degrees
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Q. A light ray strikes a glass surface at an angle of incidence of 30 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?
A.
20 degrees
B.
30 degrees
C.
40 degrees
D.
50 degrees
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Solution
Using Snell's law, n1 * sin(θ1) = n2 * sin(θ2). Here, n1 = 1 (air), θ1 = 30 degrees, n2 = 1.5. Thus, sin(θ2) = (1 * sin(30))/1.5 = 1/3, giving θ2 ≈ 20 degrees.
Correct Answer: A — 20 degrees
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Q. A ray of light passes from air into glass at an angle of incidence of 30 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?
A.
20 degrees
B.
30 degrees
C.
18.4 degrees
D.
22 degrees
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Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). Here, n1 = 1 (air), i = 30 degrees, n2 = 1.5 (glass). Thus, sin(r) = (1 * sin(30))/1.5 = 0.333, giving r ≈ 18.4 degrees.
Correct Answer: C — 18.4 degrees
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Q. A ray of light passes from air into glass at an angle of incidence of 45 degrees. If the refractive index of glass is 1.5, what is the angle of refraction?
A.
30 degrees
B.
45 degrees
C.
60 degrees
D.
90 degrees
Show solution
Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). Here, n1 = 1 (air), n2 = 1.5 (glass), i = 45 degrees. Solving gives r = 30 degrees.
Correct Answer: A — 30 degrees
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Q. A ray of light passes through the center of curvature of a concave mirror. What will be the angle of reflection?
A.
0 degrees
B.
30 degrees
C.
45 degrees
D.
90 degrees
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Solution
When a ray of light passes through the center of curvature, it strikes the mirror perpendicularly, resulting in an angle of reflection of 0 degrees.
Correct Answer: A — 0 degrees
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Q. A ray of light passes through the center of curvature of a concave mirror. What is the angle of reflection?
A.
0 degrees
B.
30 degrees
C.
45 degrees
D.
90 degrees
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Solution
When a ray passes through the center of curvature, it strikes the mirror perpendicularly, resulting in an angle of reflection of 0 degrees.
Correct Answer: A — 0 degrees
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Q. A ray of light passes through the optical center of a lens. What happens to the ray?
A.
It bends towards the normal
B.
It bends away from the normal
C.
It continues in a straight line
D.
It reflects back
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Solution
A ray of light passing through the optical center of a lens continues in a straight line without bending.
Correct Answer: C — It continues in a straight line
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Q. A ray of light strikes a plane mirror at an angle of 30 degrees. What is the angle of reflection?
A.
30 degrees
B.
60 degrees
C.
90 degrees
D.
45 degrees
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Solution
According to the law of reflection, the angle of reflection is equal to the angle of incidence, which is 30 degrees.
Correct Answer: A — 30 degrees
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Q. A ray of light strikes a plane mirror at an angle of incidence of 30 degrees. What is the angle of reflection?
A.
30 degrees
B.
45 degrees
C.
60 degrees
D.
90 degrees
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Solution
According to the law of reflection, the angle of reflection is equal to the angle of incidence. Therefore, the angle of reflection is 30 degrees.
Correct Answer: A — 30 degrees
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Q. A ray of light traveling in air strikes the surface of water at an angle of incidence of 45 degrees. What is the angle of refraction?
A.
30 degrees
B.
45 degrees
C.
60 degrees
D.
90 degrees
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Solution
Using Snell's law, n1 * sin(i) = n2 * sin(r). For air (n1=1) and water (n2=1.33), we find r = 45 degrees.
Correct Answer: B — 45 degrees
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Q. A thin lens has a focal length of 20 cm. What is the power of the lens?
A.
+2.5 D
B.
+5 D
C.
+10 D
D.
+15 D
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Solution
Power (P) is given by P = 1/f (in meters). Thus, P = 1/0.2 = +5 D.
Correct Answer: B — +5 D
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Q. An object is placed at a distance of 15 cm from a convex lens of focal length 10 cm. Where is the image formed?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
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Solution
Using the lens formula, 1/f = 1/v - 1/u, we find v = 30 cm, meaning the image is formed 30 cm on the opposite side.
Correct Answer: D — 20 cm
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Q. An object is placed at a distance of 30 cm from a convex lens of focal length 15 cm. What is the distance of the image from the lens?
A.
10 cm
B.
15 cm
C.
20 cm
D.
30 cm
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Solution
Using the lens formula, 1/f = 1/v - 1/u. Here, f = 15 cm, u = -30 cm. Solving gives v = 10 cm.
Correct Answer: C — 20 cm
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Q. If a beam of light passes through a prism with an angle of 60 degrees and the refractive index of the prism is √3, what is the angle of minimum deviation?
A.
30 degrees
B.
60 degrees
C.
45 degrees
D.
15 degrees
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Solution
Using the formula for minimum deviation, D = (n - 1)A. Here, n = √3 and A = 60 degrees. Thus, D = (√3 - 1) * 60 degrees, which approximates to 30 degrees.
Correct Answer: A — 30 degrees
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Q. If a concave lens has a focal length of -15 cm, what is its power?
A.
-6.67 D
B.
6.67 D
C.
-15 D
D.
15 D
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Solution
Power (P) = 1/f = 1/(-0.15) = -6.67 D.
Correct Answer: A — -6.67 D
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Q. If a concave mirror has a radius of curvature of 20 cm, what is its focal length?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
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Solution
The focal length (f) of a concave mirror is half the radius of curvature (R). Therefore, f = R/2 = 20 cm / 2 = 10 cm.
Correct Answer: B — 10 cm
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Q. If a convex lens has a focal length of 15 cm, what is the power of the lens?
A.
+2.5 D
B.
+5 D
C.
+10 D
D.
+15 D
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Solution
Power (P) is given by P = 1/f (in meters). Thus, P = 1/0.15 = +6.67 D.
Correct Answer: B — +5 D
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Q. If a lens has a focal length of -20 cm, what type of lens is it?
A.
Convex lens
B.
Concave lens
C.
Biconvex lens
D.
Biconcave lens
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Solution
A negative focal length indicates that the lens is a concave lens.
Correct Answer: B — Concave lens
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Q. If a ray of light passes through the optical center of a lens, what happens to the ray?
A.
It bends towards the normal.
B.
It bends away from the normal.
C.
It continues in a straight line.
D.
It converges to a point.
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Solution
A ray of light passing through the optical center of a lens continues in a straight line without bending.
Correct Answer: C — It continues in a straight line.
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