All 20 questions from the Post-UTME Screening (Post-UTME) Physics 2018 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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Heat radiation occurs most rapidly from a surface which is
Dull, black surfaces are the best emitters (and absorbers) of thermal radiation.
The distance between two successive crests of a wave is 25.0 cm and the velocity of the wave is 275.0ms-1. What is the frequency of the wave?
Wavelength = 25.0cm = 0.25m. Frequency = v/lambda = 275/0.25 = 1100Hz.
The phenomenon that enables sound waves to travel round obstacles is
Diffraction is the bending of waves around obstacles/through openings, enabling sound to travel round obstacles.
In a hall, a sound produced may persist for some time afterwards. This phenomenon is known as
Reverberation is the persistence of sound in an enclosed space due to repeated reflections.
The sound of an electric bell cannot be heard if it is kept in an evacuated jar because the
Sound is a mechanical wave and requires a medium; it cannot travel through the vacuum inside the evacuated jar.
Which of the following gives the correct expression for the second position of resonance in a closed tube?
In a closed pipe, resonance positions occur at odd multiples of lambda/4; the second resonance position is at l = 3lambda/4.
Which condition must be fulfilled in order to obtain a sharp image of an object placed in front of a pin-hole camera?
A smaller pinhole produces a sharper (though dimmer) image by limiting the spread of light rays.
A convex mirror is usually used as a driving mirror because it
A convex mirror's diverging surface gives a wider field of view, useful for driving mirrors.
Which of the following is NOT an application of electromagnetic induction?
The Van de Graaff generator works by mechanical charge transfer (a moving belt), not electromagnetic induction.
Which of the following is CORRECT when light wave enters an optically denser medium? I. The wavelength increases. II. The wavelength decreases. III. The frequency remains constant.
When light enters a denser medium, it slows down, causing the wavelength to decrease, while frequency remains constant.
A virtual image of an object was obtained at a distance of 30.0 cm from a converging lens of focal length 20.0cm. What is the distance of the object from the lens?
For a virtual image, v=-30cm, f=20cm. Using 1/v-1/u=1/f: -1/30-1/u=1/20, giving u=-12cm, so object distance is 12.0cm.
Use the diagram above (a converging lens with 2F', F', F and 2F marked) to answer this question. Where must an object be placed so that an inverted but enlarged image can be formed?
An object placed between F and 2F (on the object side, F' and 2F') produces a real, inverted, magnified image beyond 2F on the other side.
The image formed by the objective lens of a compound microscope is usually
The objective lens of a compound microscope forms a real, inverted, magnified image, which is then further magnified by the eyepiece.
The closest point at which an object placed in front of the eye could be clearly seen is called the
The near point is the closest distance at which the eye can focus clearly on an object.
Use the figure above (three overlapping circles labelled RED, GREEN and BLUE, with the central overlap region labelled H) to answer this question. In the figure above, what is the colour of the region of intersection of the red, green and blue circles labelled H?
The overlap of all three primary colours of light (red, green and blue) produces white light.
A sheet of white paper viewed through red glass appears red because
The red glass filter transmits only red light and absorbs other wavelengths, so the white paper (reflecting all colours) appears red through it.
Which of the following statements about a charged electroscope are correct? I. when a negatively charged object is brought close to a negatively charged electroscope, the divergence increases. II. When a positively charged object is brought close to a negatively charged electroscope, the divergence decreases. III. When an uncharged object is brought close to a negatively charged electroscope, the divergence decreases.
Bringing a like (negative) charge closer increases divergence (repulsion); bringing an opposite (positive) charge closer decreases divergence; an uncharged object has negligible direct effect (statement III is not generally correct).
The ground state of an atom occurs when the electrons are
The ground state is the lowest possible energy configuration of an atom's electrons.
A neutral point in a magnetic field is defined as a point where the
A neutral point is where the resultant magnetic flux density (from all sources, including the earth's field) is zero.
The angle between the magnetic and geographic meridian is the angle of
The angle between magnetic north and true (geographic) north is called the angle of declination.
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