Question

O White
4. What is the frequency of violet colour of wavelength 4000 Å?*
O 3.75*10^14 Hz
O 7.35x10^14 Hz
O 5.7x10^14 Hz
O ^
7.5x10^14 Hz​

Answer 1

7.5 × 10¹⁴ Hz is the required answer.

Option D is right.

GIVEN:

Wavelength of violet color, λ = 4000 A°

TO FIND:

Frequency of violet color, f

FORMULA:

c = fλ

Where c is the velocity of light in free space or vacuum.

c = 3 × 10⁸ m/s

SOLUTION:

STEP 1: TO CONVERT WAVELENGTH INTO STANDARD UNITS

• SI unit of length is metre, m

• 1 A⁰ = 10^-10 m

• 4000 A⁰ = 4000 × 10^-10 m = 4 × 10³ × 10^-10 m

• Wavelength, λ = 4 × 10^-7 m

STEP 2 : TO FIND FREQUENCY

c = fλ

3 × 10⁸ = f × 4 × 10^-7

$f =\dfrac{3\times10^8}{4\times10^-7}\\\\f = \dfrac{3}{4} \times10^{8+7}\\\\f =0.75\times 10^{15}\\\\f =0.75\times 10^{15}\times\dfrac{10}{10} \\\\f =0.75\times10\times\dfrac{10^{15}}{10} \\\\f = 7.5 \times 10^{14} \:Hz$

ANSWER:

Frequency of violet color is 7.5 × 10¹⁴ Hz.

NOTES:

• Frequency is inversely proportional to the wavelength of the colour.

• Red color has the maximum wavelength and minimum frequency.

• Blue color has the maximum frequency ,since it has miminum wavelength among visible light.

Answer 2

check my answer tooo