Modern Physics Practice Questions
WAEC (West Africa) · WAEC Physics · 139 free MCQs with instant results and detailed explanations.
139
Total
42
Easy
77
Medium
20
Hard
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Sample Questions from Modern Physics
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Q1
Easy
What is the primary function of a Geiger-Muller counter?
A.
To measure electric current
B.
To detect ionizing radiation
C.
To measure temperature
D.
To amplify sound waves
Show Answer & Explanation
Correct Answer: B
A Geiger-Muller counter is specifically designed to detect and measure ionizing radiation, making option B the correct answer.
Q2
Easy
What is the primary particle found in atomic nuclei that has no charge?
A.
Proton
B.
Electron
C.
Neutron
D.
Photon
Show Answer & Explanation
Correct Answer: C
Neutrons are neutral particles found in the nucleus of an atom, unlike protons which are positively charged and electrons which are negatively charged.
Q3
Easy
In terms of energy levels, what happens when an electron jumps from a higher energy level to a lower energy level?
A.
Energy is absorbed
B.
No energy change occurs
C.
Energy is emitted
D.
Mass is converted to energy
Show Answer & Explanation
Correct Answer: C
When an electron transitions from a higher energy level to a lower one, it emits energy in the form of a photon.
Q4
Medium
What is the main principle behind the operation of a laser?
A.
Spontaneous emission of photons
B.
Stimulated emission of photons
C.
Absorption of photons
D.
Reflection of light
Show Answer & Explanation
Correct Answer: B
Lasers operate on the principle of stimulated emission of photons, which results in coherent light being produced. This is different from spontaneous emission, where photons are emitted randomly.
Q5
Medium
In a photoelectric effect experiment, light of frequency 8 x 10^14 Hz is incident on a metal surface. If the work function of the metal is 3.2 x 10^-19 J, what is the maximum kinetic energy of the emitted electrons?
A.
1.6 x 10^-19 J
B.
3.2 x 10^-19 J
C.
4.8 x 10^-19 J
D.
Zero
Show Answer & Explanation
Correct Answer: A
The maximum kinetic energy (KE) of emitted electrons can be calculated using the formula KE = hf - ฯ. Here, h (Planck's constant) = 6.63 x 10^-34 Jยทs and f = 8 x 10^14 Hz. KE = (6.63 x 10^-34 Jยทs * 8 x 10^14 Hz) - 3.2 x 10^-19 J = 1.6 x 10^-19 J.
Q6
Medium
Which particle is a primary carrier of electromagnetic force?
A.
Electron
B.
Photon
C.
Neutron
D.
Proton
Show Answer & Explanation
Correct Answer: B
The photon is the force carrier for electromagnetic interactions. It mediates the electromagnetic force between charged particles, unlike electrons, neutrons, or protons which are matter particles.
Q7
Medium
If an atom has an atomic number of 6 and mass number of 14, how many neutrons does it contain?
A.
6
B.
8
C.
14
D.
2
Show Answer & Explanation
Correct Answer: B
The number of neutrons can be calculated using the formula: Neutrons = Mass number - Atomic number. Therefore, Neutrons = 14 - 6 = 8.
Q8
Hard
A radioactive isotope has a half-life of 5 years. If you start with 80 grams of the isotope, how much will remain after 15 years?
A.
10 grams
B.
20 grams
C.
30 grams
D.
40 grams
Show Answer & Explanation
Correct Answer: A
After 15 years, which is three half-lives (5 years each), the amount of the isotope will be halved three times: 80g โ 40g โ 20g โ 10g. Therefore, 10 grams will remain.
Q9
Hard
A radioactive substance has a half-life of 5 years. If we start with 80 grams of this substance, how much will remain after 15 years?
A.
10 grams
B.
20 grams
C.
30 grams
D.
40 grams
Show Answer & Explanation
Correct Answer: A
After 15 years, which is 3 half-lives (15/5=3), the remaining quantity is 80 grams / (2^3) = 80 / 8 = 10 grams.
Q10
Hard
A certain isotope has a half-life of 10 years. If you start with 80 grams of the isotope, how much will remain after 30 years?
A.
10 grams
B.
20 grams
C.
40 grams
D.
5 grams
Show Answer & Explanation
Correct Answer: A
After 30 years, which is 3 half-lives (10, 20, and then 30 years), the remaining mass is calculated as 80g / 2^3 = 80g / 8 = 10g. Hence, 10 grams of the isotope will remain.
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Modern Physics โ WAEC (West Africa) WAEC Physics Practice Questions Online
This page contains 139 practice MCQs for the chapter Modern Physics in WAEC (West Africa) WAEC Physics. The questions are organized by difficulty โ 42 easy, 77 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.