SPSC PHYSICS 25 YEARS PAST PAPERS
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
ایک مساوی پرزم اور ہوا کا 45 ڈگری کا نازک زاویہ ہوتا ہے۔ اگر آنے والی شعاع ریفریکٹنگ سطح پر کھڑی ہے تو یہ _____؟
It keeps reflecting from all the three sides of the prism and never emerges out
It gets reflected from second and third surfaces and emerges from the first surface
It is reflected from the second surface and emerges perpendicular from the third surface
None of these
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Explanation
Total Internal Reflection (TIR) : Since the critical angle is 45° , and the incident ray is perpendicular to the first surface , it enters without deviation and strikes the second surface at 60° (greater than 45°), causing TIR . Emergence : After reflecting from the second surface, the ray reaches the third surface at 30° , which is less than the critical angle , so it emerges perpendicularly from the third surface .
4.5 × 10^7 m/s
5.5 × 10^7 m/s
8.5 × 10^10 m/s
None of these
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Explanation
Using the relativistic mass equation: m = m0 / sqrt(1 - v^2/c^2)
Rearranging to solve for v:
v ≈ sqrt(1 - (m0/m)^2) × c
Plugging in the values:
v ≈ sqrt(1 - (60/61)^2) × 3.0 × 10^8 m/s
≈ 4.5 × 10^7 m/s
کلاسیکی تھیوری کے مطابق داڑھ کی مخصوص حرارت کی قدر _____ ہے؟
R
2R
3R
None of these
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Explanation
According to the classical equipartition theorem , the molar specific heat at constant volume (Cv) : for a monatomic gas is (3/2)R for a diatomic gas is (5/2)R for a solid is 3R (Dulong-Petit law). The molar specific heat at constant pressure (Cp) for a solid is approximately 3R .
بریگ کی مساوات _____ کا نتیجہ ہے؟
Diamond structure
Schrodinger equation
Laue equations
None of these
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Explanation
Bragg's equation (nλ = 2d sinθ) is derived from Laue equations . It describe the diffraction of X-rays by crystal lattices. Max von Laue formulated these equations, which later led to Bragg's Law , explaining X-ray diffraction patterns.
0.5 × 10^-4 kgm^2
0.5 kgm^2
0.5 × 10^4 kgm^2
None of these
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Explanation
To find the moment of inertia (I) of the rotating body, we can use the formula:
τ = I × α
where τ is the torque, I is the moment of inertia, and α is the angular acceleration.
Given:
τ = 2 × 10^-4 Nm
α = 4 rad/s^2
Rearranging the formula to solve for I:
I = τ / α
= (2 × 10^-4 Nm) / (4 rad/s^2)
= 0.5 × 10^-4 kgm^2
کوانٹم نمبر _____ کے حل ہیں؟
Einstein's mass energy relation
Schrodinger's Wave Equation
Hamilton Operator
None of these
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Explanation
Quantum numbers arise as solutions to Schrödinger's wave equation . It describes the behavior of electrons in an atom. These numbers define electron properties like energy levels (n), shape (l), orientation (mₗ), and spin (mₛ).
4.5 × 10^10
4.5 × 10^9
9 × 10^9 years
None of these
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Explanation
To find the time it takes to decay 75% of the initial amount, we need to find the time it takes for 25% of the initial amount to remain.
Since the half-life is 4.5 × 10^9 years, after one half-life, 50% of the initial amount remains.
After two half-lives, 25% of the initial amount remains (50% of 50%).
Therefore, the time it takes to decay 75% of the initial amount is:
2 × half-life = 2 × 4.5 × 10^9 years = 9 × 10^9 years
270
135
35
None of these
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Explanation
To find the work done, we need to integrate the force with respect to the displacement.
Given:
F(x) = 7 - 2x + 3x^2 N
x_initial = 0 m
x_final = 5 m
Work done (W) is the integral of force (F) with respect to displacement (x):
W = ∫[x_initial, x_final] F(x) dx
= ∫[0, 5] (7 - 2x + 3x^2) dx
Evaluating the integral:
W = [7x - x^2 + x^3] from 0 to 5
= (7(5) - 5^2 + 5^3) - (7(0) - 0^2 + 0^3)
= (35 - 25 + 125) - 0
= 135 J
مقناطیسی ویکٹر کی صلاحیت ایک _____ ویکٹر ہے؟
Whose divergence is equal to electric potential
Whose curl is equal to the magnetic flux density
Whose curl is equal to the electric field intensity
None of these
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Explanation
Magnetic Vector Potential ( A mathbf{A} ) is a vector field whose curl gives the magnetic flux density ( B mathbf{B} ), expressed as:
B = ∇ × A This potential is useful in electromagnetism as it simplifies Maxwell’s equations. It is used in solving problems related to electromagnetic fields.
2.9°
1.5°
5.8°
None of these
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Explanation
To find the smallest Bragg scattering angle, we can use Bragg's law:
2d sin(θ) = nλ
where d is the distance between the atomic planes, θ is the scattering angle, n is an integer (which is 1 for the smallest angle), and λ is the wavelength of the X-ray.
Given:
d = 0.3 nm
λ = 0.03 nm
Rearranging Bragg's law to solve for θ, we get:
sin(θ) = λ / (2d)
= 0.03 nm / (2 × 0.3 nm)
= 0.05
θ = arcsin(0.05)
≈ 2.9°
