E.5 Fusion SL Paper 1- IBDP Physics 2025- Exam Style Questions

IBDP Physics SL 2025 -E.5 Fusion SL Paper 1 Exam Style Questions

Topic:E.5 Fusion SL Paper 1

Nuclear Fusion in Stars, Stellar Evolution, Stellar Parallax, Stellar Spectra

Question

The mass defect for deuterium is 4×10–30 kg. What is the binding energy of deuterium?

A. 4×10–7 eV

B. 8×10–2 eV

C. 2×10eV

D. 2×1012 eV

Markscheme

C

$$1 kg = 6.022\times 10^{-26}amu$$
so in $$4\times 10^{-30}kg=24.088\times 10^{-4}$$
$$E_b=\Delta m.c^2$$
$$\Delta m=0.0024 u$$
$$E_b=(0.0024)\times (\frac{931MEV}{c^2})\times c^2$$
$$=2.3\times 10^6 ev$$

Question

The nuclear reaction $${}_1^2{\rm{H}} + {}_1^3{\rm{H}} \to {}_2^4{\rm{He + }}{}_0^1{\rm{n}}$$ would best be described as

A. alpha decay.
B. nuclear fission.
C. nuclear fusion.
D. neutron capture.

Markscheme

C

Fusion reactions constitute the fundamental energy source of stars, including the Sun. The evolution of stars can be viewed as a passage through various stages as thermonuclear reactions and nucleosynthesis cause compositional changes over long time spans. Hydrogen (H) “burning” initiates the fusion energy source of stars and leads to the formation of helium (He). Generation of fusion energy for practical use also relies on fusion reactions between the lightest elements that burn to form helium. In fact, the heavy isotopes of hydrogen—deuterium (D) and tritium (T)—react more efficiently with each other, and, when they do undergo fusion, they yield more energy per reaction than do two hydrogen nuclei. (The hydrogen nucleus consists of a single proton. The deuterium nucleus has one proton and one neutron, while tritium has one proton and two neutrons.)

Question

Bismuth-210 $$\left( {_{\;83}^{210}{\text{Bi}}} \right)$$ is a radioactive isotope that decays as follows.

$_{\;83}^{210}{\text{Bi}}\xrightarrow{{{\beta ^ – }}}{\text{X}}\xrightarrow{\alpha }{\text{Y}}$

What are the mass number and proton number of Y?

Markscheme

B

Bismuth-210 decays to polonium-210 through a beta decay.

alpha decay of polonium-210-

Question

The graph shows the relationship between binding energy per nucleon and nucleon number. In which region are nuclei most stable?

Markscheme

C

The graph of binding energy per nucleon with mass number A is as shown below.
Binding energy per nucleon gives a measure of stability of nucleus. More is binding energy per nucleon more is the stability of nucleus. Binding energy per nucleon is small for lighter nuclei
i.e. 1H1, 1H2  etc.
For A < 28 at A = 4n the curve shows some peaks at 2He4, 4Be8, 6C16, 8O16, 10Ne20, 12Mg24 .
This represents extra stability of these elements with respect to their neighbours.
Question

A sample contains an amount of radioactive material with a half-life of 3.5 days. After 2 weeks the fraction of the radioactive material remaining is

A.     94 %.

B.     25 %.

C.     6 %.

D.     0 %.

Markscheme

C

$$t_{\frac{1}{2}}=$$3.5 days
in two weeks 14 dyas $$=4t_{\frac{1}{2}}$$
Material reamining after $$n$$ half life $$=\frac{A_o}{2^n}$$
$$A_o =$$ initial amount
After 4 half-life $$= \frac{A_o}{2^4}\rightarrow \frac{A_o}{16}$$
%age remaining $$=\frac{A_o/16}{A_o}\times 100$$
$$=6.25%$$

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