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Physics
WAEC / WASSCE 2004
Modern Physics and Nuclear Physics
Which of the following statements about X-rays is not correct? They
A
are electromagnetic waves
B
can be used to study crystal lattice
C
can destroy living cells
D
are produced from the nucleus of an atom
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #34407)
Physics
WAEC / WASSCE 2004
Modern Physics and Nuclear Physics
Solution
A radioactive substance has a half-life of 3 days. If a mass of 1.55g of this substance is left after decaying for 15 days, determine the original value of the mass
A
49.6g
B
37.2g
C
24.8g
D
12.4g
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(1 \to \frac{1}{2} \to \frac{1}{4} \to \frac{1}{8} \to \frac{1}{16} \to \frac{1}{32}\)
\(\frac{1}{32} = 1.55g\)
1 = 1.55 x \(\frac{32}{1} = 49.6g\)
Source: Myschool Past Questions Archive (Record #34411)
Physics
NECO SSCE 2004
Modern Physics and Nuclear Physics
A radioactive isotope has a half-life of 8 days. What fraction of the atoms will remain after 72 days?
A
9.766 × 10-4
B
1.736 ×10-3
C
1.953 ×10-3
D
3.472 × 10-3
E
3.906 x 10-3
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #42989)
Physics
UTME / JAMB 2003
Modern Physics and Nuclear Physics
Solution
The count rate of a radioactive material is 800 count/min. If the half-life of the material is 4 days, what would the count rate be in 16 days later
A
200 count / min
B
100 count / min
C
50 count / min
D
25 count / min
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
116 days = 4 half - lives
Thus, after 4 half lives the fraction left of any radioactive materials is given by (1/2)4 = 1/16
∴ Count rate / amount left = 1/16 x 800/1
= 50 count / min
Source: Myschool Past Questions Archive (Record #12749)
Physics
WAEC / WASSCE 2003
Modern Physics and Nuclear Physics
Solution
A metal rod of length 100cm is heated through 100ºC, calculate the change in length of the rod [linear expansivity of the material of the rod is 3 x 10\(^{-5}\)K\(^{-1}\)]
A
4mm
B
3mm
C
2mm
D
1mm
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
\(I_2 - I_1 = I_1 \times \theta \times \alpha = 1 \times 100 \times 3 \times 10^{-5}\)
= 3 x 10\(^{-3}\)m
= 3mm
Source: Myschool Past Questions Archive (Record #34210)
Physics
WAEC / WASSCE 2003
Modern Physics and Nuclear Physics
Solution
A radioactive element has a decay constant of 0.077s-1, calculate its half life
A
12.5s
B
9.0s
C
5.1s
D
0.5s
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
T = \(\frac{0.692}{\lambda} = \frac{0.692}{0.077}\)
= 9s
Source: Myschool Past Questions Archive (Record #34240)
Physics
NECO SSCE 2003
Modern Physics and Nuclear Physics
Solution
In 90 seconds, the mass of a radioactive element reduces to \(\frac{1}{16}\) of its original value. Determine the half- life of the element.
A
15.0s
B
18.0s
C
22.5s
D
30.0s
E
45.0s
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
\(\frac{1}{16} = (\frac{1}{2})^n\)
\((\frac{1}{2})^4 = (\frac{1}{2})^n\)
\(n = 4\)
90 secs = 4 half lives
1 half life = \(\frac{90}{4}\) secs
= 22.5 secs
Source: Myschool Past Questions Archive (Record #42932)
Physics
UTME / JAMB 2002
Modern Physics and Nuclear Physics
Solution
The percentage of the original nuclei of the sample of a radioactive substance left after 5 half - lives is
A
8%
B
5%
C
3%
D
1%
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
After 5 half-lives, the fraction of any radio-active substance left = (1/2)5 = 1/32
Thus the percentage of the original nuclei = 1/32/1 x 100/1
assuming the original amount is unity percentage left
= 1/32 x 100/1 = 3.12 = 3%
Source: Myschool Past Questions Archive (Record #12256)
Physics
WAEC / WASSCE 2002
Modern Physics and Nuclear Physics
A nuclide X is produced by bombarding a nitrogen(N) nucleus with an alpha(\alpha\) particle with the release of heavy hydrogen(D) nucleus as shown by the following nuclear equation, \(\alpha + ^{14}_{7}N \to ^p_qX + ^2_1D\). Determine the values of p and q in the equation
A
12 and 6
B
14 and 7
C
16 and 8
D
19 and 8
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #34148)
Physics
WAEC / WASSCE 2002
Modern Physics and Nuclear Physics
If a radioactive atom emits a beta particle, Its mass number
A
increases by one
B
remains the same
C
decreases by one
D
increases by two
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #34144)
Physics
WAEC / WASSCE 2002
Modern Physics and Nuclear Physics
Which of the following is usually used to cause fission in an atomic reactor?
A
Alpha particles
B
beta particles
C
electrons
D
Neutrons
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #34145)
Physics
NECO SSCE 2002
Modern Physics and Nuclear Physics
In an operating X-ray tube, a high p.d is applied between the cathode and the anode for the purpose of
A
accelerating the electrons to a very high energy
B
concentrating electrons on the target
C
heating the anode
D
heating the cathode
E
producing a stream of electrons
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #42857)
Physics
NECO SSCE 2002
Modern Physics and Nuclear Physics
Solution
A brass cube of side 10cm is heated through 30^\circC. If the linear expansivity of brass is 2.0 \times I0\(^{-5}\) K-1 , what is the increase in its volume?
A
0.06 cm3
B
0.18cm3
C
0.60cm3
D
1.20cm3
E
1.80cm3
medium Difficulty
Verified Correct Answer: Option E
Physical Principles & Numerical Solution
cubic expansivity and γ = 3\alpha. → 3 * 2.0 \times I0\(^{-5}\)
cubic expansivity = 6.0 \times I0\(^{-5}\) , Ø = 30^\circC,
Volume(v\(_1\)) = L\(^3\) = 10\(^3\) → 1000
V\(_2\) = V\(_1\)(1 + γ\theta)
→ V\(_2\) = 1000[1 + 6.0 \times I0\(^{-5}\) * 30]
= 1000[1 + 0.0018]
= 1000 * 1.0018 → 1,001.8
increase in volume = 1,001.8 - 1000
→ 1.8cm\(^3\)
Source: Myschool Past Questions Archive (Record #42868)
Physics
UTME / JAMB 2001
Modern Physics and Nuclear Physics
Diagram
Solution
If ray travelling in air is incident on a transparent medium as shown in the diagram, the refractive index of the medium is given as
Attached Figure / Diagram
A
cosα / sinβ
B
sinα / sinβ
C
cosβ / sinα
D
sinβ / sinα
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(n = \frac{sin i}{sin r}\)
\(i = 90 - \alpha\)
\(\therefore n = \frac{sin 90 - \alpha}{sin \beta}\)
⇒ \(n = \frac{cos \alpha}{sin \beta}\)
Source: Myschool Past Questions Archive (Record #11828)
Physics
WAEC / WASSCE 2001
Modern Physics and Nuclear Physics
Solution
Production of x-ray tube begins with
A
photo electric emission
B
collision of electrons
C
thermionic emission
D
field emission of electrons
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
The production of X-rays in an X-ray tube begins with thermionic emission from the hot cathode.
Source: Myschool Past Questions Archive (Record #33946)