Post Utme Physics Past Questions and Answers

Question 581:

An object is placed \(20 \mathrm{~cm}\) in} front of a concave mirror whose focal length is \(10 \mathrm{~cm}\). where and how is the image formed?

A. Center of curvature and inverted
B. \(20 \mathrm{~cm}\) behind the mirror and inverted
C. \(20 \mathrm{~cm}\) in front of the mirror and upright
D. \(20 \mathrm{~cm}\) in front of the mirror and virtual

Question 582:

Caesium has a work function of \(3 \times 10^{19} \mathrm{~J}\), the maximum energy of liberated electrons when it is illuminated by light of frequency \(6.7 \times 10^{14} \mathrm{~Hz}\) is ____________

\(\left.\left[h=6.67 \times 10^{-34} \right] \right]\)

A. \(1.47 \times 10^{-19} \mathrm{~J}\)
B. \(3.00 \times 10^{-19} \mathrm{~J}\)
C. \(4.42 \times 10^{-19} \mathrm{~J}\)
D. \(6.6 \times 10^{-19} \mathrm{~J}\)

Question 583:

Given that Young's modulus for aluminium is \(7.0 \times 10^{10} \mathrm{Nm}^{-2}\) and density is \(2.7 \times 10^{3} \mathrm{kgm}^{-1}\), find the speed of sound produced if a solid bar is truck at one end of the hammer.

A. \(3.6 \times 10^{3} \mathrm{~ms}^{-1}\)
B. \(5.1 \times 10^{3} \mathrm{~ms}^{-1}\)
C. \(2.8 \times 10^{3} \mathrm{~ms}^{-1}\)
D. \(4.2 \times 10^{3} \mathrm{~ms}^{-1}\)

Question 584:

If \(1.2 \times 10^{6} \mathrm{~J}\) of heat energy is given off in \(1 \mathrm{sec}\) from a vessel maintained at a temperature gradient of \(30 \mathrm{~km}^{-1}\), the surface area of the vessel is ____________

[Thermal capacity of the vessel \(=\) \(400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}\) ]

A. \(1.0 \times 10^{3} \mathrm{~m}^{2}\)
B. \(1.0 \times 10^{2} \mathrm{~m}^{2}\)
C. \(9.0 \times 10^{4} \mathrm{~m}^{2}\)
D. \(9.0 \times 10^{2} \mathrm{~m}^{2}\)

Question 585:

Light ray is incident on airglass interface at angle of \(70^{\circ}\) to the interphase. Given that the refractive index of glass \((n)\) is \(1.45\), what refractive angle will the ray make with the normal?

A. \(40.41^{\circ}\)
B. \(20.71^{\circ}\)
C. \(20.17^{\circ}\)
D. \(18.97^{\circ}\)
E. \(25.00^{\circ}\)