Question

The wavelength of red light is 6500A. If velocity of light is 3x 10power 8m/s, then its time
period is ...
A) 1.62x10-15
B) 2.16x10-15
C) 2.76x10-15 D) 1.16*10-15
​

Answer 1

Answer:-

Time period is 2.16 × 10⁻¹⁵ [Option.B]

Explanation:-

We have :-

→ Wavelength of red light = 6500 Å

= 6.5 × 10⁻⁷ m

→ Velocity of light = 3 × 10⁸ m/s

________________________________

Firstly let's calculate the frequency of the red light. We know that :-

ν = c/λ

⇒ ν = [3×10⁸]/[6.5×10⁻⁷]

⇒ ν = 0.46 × 10¹⁵

⇒ ν = 4.6 × 10¹⁴ Hz

Now :-

T = 1/ν

⇒ T = 1/[4.6 × 10¹⁴]

⇒ T = 0.216 × 10⁻¹⁴

⇒ T = 2.16 × 10⁻¹⁵ second

Answer 2

Answer:-

Time period is 2.16 × 10⁻¹⁵ [Option.B]

Explanation:-

We have :-

→ Wavelength of red light = 6500 Å

= 6.5 × 10⁻⁷ m

→ Velocity of light = 3 × 10⁸ m/s

________________________________

Firstly let's calculate the frequency of the red light. We know that :-

ν = c/λ

⇒ ν = [3×10⁸]/[6.5×10⁻⁷]

⇒ ν = 0.46 × 10¹⁵

⇒ ν = 4.6 × 10¹⁴ Hz

Now :-

T = 1/ν

⇒ T = 1/[4.6 × 10¹⁴]

⇒ T = 0.216 × 10⁻¹⁴

⇒ T = 2.16 × 10⁻¹⁵ second