UAF ENTRY TEST PAST PAPER 16-07-2021 A
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
Completely filled valence band
Empty valance band
Half-filled valance band
None of these
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Explanation
An insulator has a c ompletely filled valence band.
Explanation: In an insulator, all the valence electrons are tightly bound to their atoms and cannot move freely, resulting in a filled valence band.
Since there are no electrons available in the conduction band, they cannot move to it and conduct electricity.
Semiconductor
Good conductor
Good Insulator
None of these
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Explanation
A semiconductor has electrical conductivity between that of a conductor and an insulator , and s ilicon falls within this category
Interference
Diffraction
Polarization
Photoelectric effect
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Explanation
The photoelectric effect best explains the particle nature of light.
The photoelectric effect is a phenomenon where electrons are ejected from a metal surface when exposed to light of a specific frequency. This can only be explained by considering light as composed of discrete particles called photons , each carrying a specific amount of energy. When a photon interacts with an electron in the metal, it transfers its energy to the electron, allowing it to escape the surface.
One angle
Two angles
Three angles
No angle
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Explanation
The direction of a vector in space is typically specified by three angles.
These angles, often referred to as azimuth, elevation, and tilt (or polar/inclination), describe the vector's orientation in 3D space relative to a chosen reference frame.
15 cm
25 cm
30 cm
40 cm
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Explanation
The least distance of distinct vision for a normal human eye is 25 cm.
This means that when an object is placed at a distance of 25 cm or more from the eye, a clear and distinct image is formed on the retina.
Periodic motion
Random motion
Projectile motion
None of these
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Explanation
Simple harmonic motion (SHM) is also known as oscillatory motion or periodic motion.
It can also be referred to as harmonic oscillation.
It is a system exhibiting SHM that is often c alled a simple harmonic oscillator.
Conductors
Semi-Conductors
Insulator
All of these
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Explanation
In semiconductors, when an electron leaves its position in the valence band, it creates a "hole" which can act as a positive charge carrier.
This is why holes are primarily associated with semiconductors .
Worse
Worst
Most worst
Bad
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Explanation
That was the worst movie I have ever seen.
"Worst" is the superlative form of " bad " and is used to describe something that is the worst out of a group or over time.
The phrase "I have ever seen" indicates a comparison over all time, which requires a superlative form.
For
Against
With
To
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Explanation
The brave do not yield to the enemy.
بہادر دشمن کے سامنے نہیں جھکتے۔
"Yield to" is a common phrase meaning to surrender or give in to someone or something.
In this sentence, it means the brave do not surrender to the enemy .
To
In
On
At
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Explanation
اس کی بیماری اسے بستر تک محدود کر دیتی ہے۔
"His sickness confines him to bed."
"Confine to" is the correct phrase, meaning to restrict or limit someone within certain boundaries — in this case, to the bed.
The phrase "confined to bed" is a standard expression when someone is bedridden due to illness.
