Optics Practice Questions
HSC/SSC (Bangladesh) · HSC Physics · 147 free MCQs with instant results and detailed explanations.
147
Total
43
Easy
78
Medium
26
Hard
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Sample Questions from Optics
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Q1
Easy
What happens to light when it passes from a denser medium to a rarer medium?
A.
It slows down and bends towards the normal
B.
It speeds up and bends away from the normal
C.
It is completely absorbed
D.
It reflects back into the denser medium
Show Answer & Explanation
Correct Answer: B
When light travels from a denser medium (like water) to a rarer medium (like air), it speeds up and bends away from the normal. This is due to the change in speed of light in different media.
Q2
Easy
What is the focal length of a concave lens if its focal point is 20 cm from the lens?
A.
-20 cm
B.
20 cm
C.
10 cm
D.
-10 cm
Show Answer & Explanation
Correct Answer: A
The focal length of a concave lens is considered negative. Thus, if the focal point is located 20 cm from the lens, the focal length is -20 cm.
Q3
Easy
Which of the following statements is true regarding total internal reflection?
A.
It can occur when light travels from a rarer to a denser medium
B.
It requires the angle of incidence to be less than the critical angle
C.
It occurs only in optical fibers
D.
It can occur when light travels from a denser to a rarer medium
Show Answer & Explanation
Correct Answer: D
Total internal reflection occurs when light travels from a denser medium (like glass) to a rarer medium (like air) at an angle greater than the critical angle, causing it to reflect completely back into the denser medium.
Q4
Medium
What happens to the focal length of a convex lens when it is immersed in water?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes infinite
Show Answer & Explanation
Correct Answer: B
The focal length of a convex lens decreases when immersed in water because the refractive index of water is less than that of the lens material, leading to a change in the lens's optical power.
Q5
Medium
In an optical fiber, total internal reflection occurs when the angle of incidence is greater than which critical angle for a medium with a refractive index of 1.5?
A.
30 degrees
B.
42 degrees
C.
48 degrees
D.
60 degrees
Show Answer & Explanation
Correct Answer: B
The critical angle ฮธc can be calculated using the formula ฮธc = sin^(-1)(1/n), which gives approximately 42 degrees for a refractive index of 1.5.
Q6
Medium
A beam of light traveling in air 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.
50 degrees
D.
60 degrees
Show Answer & Explanation
Correct Answer: B
Using Snell's Law (n1 * sin(ฮธ1) = n2 * sin(ฮธ2)), we can find that the angle of refraction is 40 degrees when the light enters the glass from air.
Q7
Medium
A concave mirror forms a real image of an object placed 30 cm in front of it. If the image distance is 20 cm, what is the focal length of the mirror?
A.
10 cm
B.
15 cm
C.
5 cm
D.
20 cm
Show Answer & Explanation
Correct Answer: B
The focal length (f) can be found using the mirror formula: 1/f = 1/v + 1/u. Here, v = -20 cm (real image) and u = -30 cm (object distance). Thus, 1/f = 1/(-20) + 1/(-30) = -1/12. Therefore, f = 15 cm.
Q8
Hard
A lens has a focal length of 20 cm. An object is placed 30 cm from the lens. What is the position of the image formed by the lens?
A.
60 cm on the same side as the object
B.
60 cm on the opposite side
C.
12 cm on the same side as the object
D.
12 cm on the opposite side
Show Answer & Explanation
Correct Answer: B
Using the lens formula 1/f = 1/v - 1/u, where f = 20 cm, u = -30 cm (object distance is negative), we find v = 60 cm. This means the image is formed 60 cm on the opposite side of the lens.
Q9
Hard
A beam of light passes through two prisms of the same material, each with a refracting angle of 30 degrees. If the angle of incidence on the first prism is 45 degrees, what is the angle of deviation for the combined prisms?
A.
60 degrees
B.
90 degrees
C.
30 degrees
D.
120 degrees
Show Answer & Explanation
Correct Answer: A
The angle of deviation for a single prism can be calculated using the formula D = i + r - A. For each 30-degree prism and 45-degree incidence, the deviation for each prism is 30 degrees, leading to a total deviation of 60 degrees for two prisms.
Q10
Hard
A concave lens has a focal length of -15 cm. An object is placed 10 cm in front of the lens. Where will the image be formed?
A.
-6 cm
B.
-10 cm
C.
6 cm
D.
10 cm
Show Answer & Explanation
Correct Answer: A
The image distance (v) can be calculated using the lens formula 1/f = 1/v + 1/u. Here, f = -15 cm, u = -10 cm. Solving gives v = -6 cm, indicating that the image is formed 6 cm on the same side as the object.
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Optics โ HSC/SSC (Bangladesh) HSC Physics Practice Questions Online
This page contains 147 practice MCQs for the chapter Optics in HSC/SSC (Bangladesh) HSC Physics. The questions are organized by difficulty โ 43 easy, 78 medium, 26 hard โ so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.