Question

The frequency range of visible light is from $3.75\times {10}^{14}Hz$ to $7.5\times {10}^{14}Hz$. Calculate its wavelength range. Take speed of light $=3\times {10}^{8}m{s}^{-1}$.

• A. $400A^o$ to $800A^o$
• B. $40000A^o$ to $80000A^o$
• C. $4000A^o$ to $8000A^o$
• D. None of the above

Answer 1

Answer: (C)

$4000A^o$ to $8000A^o$

we know,
$\lambda \nu$$=c$
$\lambda$$=$$\frac{c}{v}$
or $=$$\frac{3\times {10}^8}{3.75\times {10}^{14}}$
or $=$8$\times {10}^{-7}$m
we know
1$A^0$$=$${10}^{-10}$
so,$=$8$\times {10}^{-7}$$\times \frac{{10}^{-3}}{{10}^{-3}}$$=$8000$A^0$
again,
$\lambda \nu$$=c$
$\lambda$$=$$\frac{c}{v}$
or $=$$\frac{3\times {10}^8}{7.5\times {10}^{14}}$
or $=$4$\times {10}^{-7}$m
we know
1$A^0$$=$${10}^{-10}$
so,$=$4$\times {10}^{-7}$$\times \frac{{10}^{-3}}{{10}^{-3}}$$=$4000$A^0$
hence,the wavelength range is from 4000$A^0$ to 8000$A^0$