Física - Óptica e Ondas Practice Questions
ENEM (Brazil) · ENEM Ciências da Natureza · 144 free MCQs with instant results and detailed explanations.
144
Total
50
Easy
76
Medium
18
Hard
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Sample Questions from Física - Óptica e Ondas
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Q1
Easy
What happens to the speed of light when it passes from air into water?
A.
It increases.
B.
It decreases.
C.
It remains constant.
D.
It becomes unpredictable.
Show Answer & Explanation
Correct Answer: B
When light enters a denser medium like water from air, its speed decreases due to the higher refractive index of water compared to air.
Q2
Easy
What is the phenomenon called when light bends while passing through a prism?
A.
Reflection
B.
Refraction
C.
Diffraction
D.
Dispersion
Show Answer & Explanation
Correct Answer: B
Refraction is the bending of light as it passes from one medium to another with a different density, which occurs in a prism.
Q3
Easy
What is the principle that describes how light waves can bend when they pass from one medium to another?
A.
Reflection
B.
Refraction
C.
Diffraction
D.
Dispersion
Show Answer & Explanation
Correct Answer: B
Refraction is the bending of light as it passes from one medium to another due to a change in its speed. This is the correct principle that describes the behavior of light in different media.
Q4
Medium
A sound wave travels through air at a speed of 340 m/s. If the frequency of the sound is 680 Hz, what is the wavelength of the sound wave?
A.
0.5 m
B.
1 m
C.
2 m
D.
0.25 m
Show Answer & Explanation
Correct Answer: A
The wavelength λ can be calculated using the formula λ = v/f. Substituting the values gives λ = 340 m/s / 680 Hz = 0.5 m.
Q5
Medium
If a convex lens has a power of +5 diopters, what is the focal length of the lens in meters?
A.
0.2 m
B.
2 m
C.
0.5 m
D.
1 m
Show Answer & Explanation
Correct Answer: A
Power (P) is defined as P = 1/f (in meters). Given P = +5 diopters, rearranging gives f = 1/P = 1/5 = 0.2 m.
Q6
Medium
A student measures the angle of incidence and angle of refraction as 45 degrees and 30 degrees, respectively, while light travels from glass to air. What can be inferred about the refractive index of glass?
A.
It is greater than 1.5
B.
It is equal to 1.5
C.
It is less than 1.5
D.
It is 1.0
Show Answer & Explanation
Correct Answer: A
Using Snell’s law, n = sin(theta1) / sin(theta2). Here, sin(45) / sin(30) gives a refractive index greater than 1.5, confirming glass is denser than air.
Q7
Medium
A beam of light passes from air into water at an angle of incidence of 30 degrees. What is the angle of refraction in water? (Refractive index of air ≈ 1, water ≈ 1.33)
A.
22.4 degrees
B.
30 degrees
C.
48.8 degrees
D.
22.1 degrees
Show Answer & Explanation
Correct Answer: A
Using Snell's Law (n1 * sin(theta1) = n2 * sin(theta2)), we find that sin(theta2) = (n1/n2) * sin(theta1). Calculating this gives us an angle of approximately 22.4 degrees for water.
Q8
Hard
A sound wave travels through air at a speed of 340 m/s. If the frequency of the sound wave is 680 Hz, what is the wavelength of the sound wave?
A.
0.5 m
B.
1.0 m
C.
2.0 m
D.
1.5 m
Show Answer & Explanation
Correct Answer: A
The wavelength (λ) can be calculated using the formula λ = v/f, where v is the speed of sound and f is the frequency. Substituting the values gives λ = 340 m/s / 680 Hz = 0.5 m.
Q9
Hard
A beam of light travels from air into water at an angle of 30 degrees to the normal. If the refractive index of water is 1.33, what is the angle of refraction in water?
A.
22.4 degrees
B.
30 degrees
C.
45 degrees
D.
23.5 degrees
Show Answer & Explanation
Correct Answer: A
Using Snell's Law, n1 * sin(theta1) = n2 * sin(theta2), we can calculate that sin(theta2) = (1.0 * sin(30 degrees)) / 1.33, which gives theta2 approximately equal to 22.4 degrees.
Q10
Hard
A sound wave travels through air at a speed of 343 m/s. If the frequency of the sound wave is 256 Hz, what is the wavelength of the sound wave?
A.
1.34 meters
B.
0.86 meters
C.
2.00 meters
D.
0.75 meters
Show Answer & Explanation
Correct Answer: A
The wavelength can be calculated using the formula: wavelength = speed / frequency. Thus, wavelength = 343 m/s / 256 Hz = 1.34 meters.
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Física - Óptica e Ondas — ENEM (Brazil) ENEM Ciências da Natureza Practice Questions Online
This page contains 144 practice MCQs for the chapter Física - Óptica e Ondas in ENEM (Brazil) ENEM Ciências da Natureza. The questions are organized by difficulty — 50 easy, 76 medium, 18 hard — so you can choose the right level for your preparation.
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