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 ____________

$[h=6.67\times {10}^{-34}]]$

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 $1\sec$ 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. ${25.00}^{\circ }$