Practice Pakistan questions with answers and explanations.
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Light changes speed when moving between media.
This speed change usually causes bending, called refraction.
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Metal structures expand in hot weather.
Gaps prevent buckling and structural damage.
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Light from the submerged part changes direction when leaving water.
The brain traces rays backward and sees an apparent displacement.
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Melting occurs when a solid gains enough energy to become liquid.
It happens at the melting point under fixed pressure.
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Spectacle lenses change the convergence of light entering the eye.
They help focus images correctly on the retina.
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Freezing removes energy from a liquid until it forms a solid.
For pure water at standard pressure, this occurs at 0°C.
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The iris changes the size of the pupil.
This regulates how much light enters the eye.
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Evaporation occurs at the surface of a liquid.
Higher temperature and moving air usually increase its rate.
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The lens focuses incoming light onto the retina.
Photoreceptor cells then convert light into nerve signals.
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Condensation occurs when gas particles lose energy.
Water vapor condenses into droplets on a cool surface.
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Red light has the longest wavelength in the visible spectrum.
Violet has the shortest visible wavelength.
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The highest-energy water molecules escape during evaporation.
This lowers the average energy and temperature of the skin.
