Optik Practice Questions
UN (Indonesia) · UN Fisika · 142 free MCQs with instant results and detailed explanations.
142
Total
48
Easy
74
Medium
20
Hard
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Sample Questions from Optik
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
What is the primary reason a prism disperses white light into its constituent colors?
A.
Refraction of light at different angles
B.
Reflection of light within the prism
C.
Diffraction of light waves
D.
Absorption of specific wavelengths
Show Answer & Explanation
Correct Answer: A
A prism disperses white light due to refraction, which bends light at different angles based on its wavelength, resulting in a spectrum of colors.
Q2
Easy
If the focal length of a concave lens is -20 cm, what is the nature of the image formed by this lens when an object is placed at 30 cm from the lens?
A.
Real and inverted
B.
Virtual and upright
C.
Real and upright
D.
Virtual and inverted
Show Answer & Explanation
Correct Answer: B
A concave lens always forms a virtual and upright image for any object placed in front of it, regardless of the distance.
Q3
Easy
Which color of light travels fastest in a vacuum?
A.
Red
B.
Green
C.
Blue
D.
All colors travel at the same speed
Show Answer & Explanation
Correct Answer: D
In a vacuum, all colors of light, regardless of wavelength, travel at the same speed, which is the speed of light (approximately 299,792 km/s).
Q4
Medium
What happens to the focal length of a lens when it is submerged in water compared to its focal length in air?
A.
It decreases.
B.
It increases.
C.
It remains the same.
D.
It becomes zero.
Show Answer & Explanation
Correct Answer: A
The focal length of a lens decreases when submerged in water due to the increase in the refractive index of the surrounding medium, which reduces the lens's bending power.
Q5
Medium
A light ray strikes a plane mirror at an angle of incidence of 30 degrees. What is the angle of reflection?
A.
15 degrees
B.
30 degrees
C.
45 degrees
D.
60 degrees
Show Answer & Explanation
Correct Answer: B
According to the law of reflection, the angle of incidence is equal to the angle of reflection. Therefore, if the angle of incidence is 30 degrees, the angle of reflection is also 30 degrees.
Q6
Medium
A student observes that a pencil appears bent when partially submerged in a glass of water. What is the reason for this phenomenon?
A.
Refraction of light.
B.
Reflection of light.
C.
Absorption of light.
D.
Diffraction of light.
Show Answer & Explanation
Correct Answer: A
The bending of the pencil appears due to refraction, which occurs when light travels from air to water, changing speed and direction.
Q7
Medium
What is the critical angle for light traveling from water (n=1.33) to air (n=1.00)?
A.
48.6 degrees
B.
42.0 degrees
C.
53.1 degrees
D.
60.0 degrees
Show Answer & Explanation
Correct Answer: A
The critical angle can be calculated using the formula sin(ฮธc) = n2/n1, where n1 is the refractive index of water and n2 is that of air. This calculation yields a critical angle of approximately 48.6 degrees.
Q8
Hard
A lens has a focal length of 15 cm. If an object is placed 30 cm away from the lens, what is the position of the image formed by the lens?
A.
30 cm on the opposite side
B.
15 cm on the same side
C.
10 cm on the opposite side
D.
45 cm on the same side
Show Answer & Explanation
Correct Answer: A
Using the lens formula, 1/f = 1/v - 1/u, where f = 15 cm and u = -30 cm (object distance is negative). Solving gives v = 30 cm on the opposite side, meaning the image is formed there.
Q9
Hard
A beam of light enters a glass prism with a refractive index of 1.5 at an angle of incidence of 30 degrees. What is the angle of refraction inside the prism?
A.
19.1 degrees
B.
20.2 degrees
C.
25.0 degrees
D.
18.4 degrees
Show Answer & Explanation
Correct Answer: A
Using Snell's Law (n1 * sin(theta1) = n2 * sin(theta2)), where n1 = 1 (air), theta1 = 30 degrees, and n2 = 1.5 (prism). Thus, sin(theta2) = (1 * sin(30)) / 1.5 = 0.3333, which gives theta2 = 19.1 degrees, making option A correct.
Q10
Hard
A concave mirror has a focal length of 10 cm. An object is placed 15 cm in front of the mirror. Where will the image be formed?
A.
30 cm in front of the mirror
B.
7.5 cm in front of the mirror
C.
7.5 cm behind the mirror
D.
30 cm behind the mirror
Show Answer & Explanation
Correct Answer: A
Using the mirror formula (1/f = 1/v + 1/u), where f = -10 cm (concave), u = -15 cm (object distance). Rearranging gives v = 30 cm, indicating the image is formed 30 cm in front of the mirror, making option A correct.
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Optik โ UN (Indonesia) UN Fisika Practice Questions Online
This page contains 142 practice MCQs for the chapter Optik in UN (Indonesia) UN Fisika. The questions are organized by difficulty โ 48 easy, 74 medium, 20 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.