Question

The wavelength range of the visible spectrum extends from violet (400 nm) to red (750 nm). Express these wavelength in frequencies (Hz). $(1nm={10}^{-9}m)$.

• A. $4\times {10}^{14}to7.5\times {10}^{14}Hz$
• B. $8\times {10}^{14}to16\times {10}^{14}Hz$
• C. $7\times {10}^{14}to16\times {10}^{14}Hz$
• D. $7.5\times {10}^{14}to16\times {10}^{14}Hz$

Answer 1

The correct option is A

$4\times {10}^{14}to7.5\times {10}^{14}Hz$

We know that,
$v=\frac{c}{\lambda }$
Now, frequency of violet light is:
$v=\frac{c}{\lambda }=\frac{3.00\times {10}^{8}m{s}^{-1}}{400\times {10}^{-9}m}=7.50\times {10}^{14}Hz$

Frequency of red light is:
$v=\frac{c}{\lambda }=\frac{3.00\times {10}^{8}m{s}^{-1}}{750\times {10}^{-9}m}=4.00\times {10}^{14}Hz$

The range of visible spectrum is from $4.0\times {10}^{14}Hz$ in terms of frequency units.