Question

Calculate the power per unit area delivered by a laser pulse of energy 4 103 joule and pulse length as 109 sec when the pulse is focused on target to a very small spot of radius 1.5 105m.

Answer 1

Answer:0.5661*10^16Watt/m2

Explanation:

Peak Power=Pulsed Energy/Duration

And power per unit area=Peak Power/3.14*radius*radius

Put all the values and just find out answer given.

It is a effort by me but still confirm and do yourself.

Answer 2

Answer:

The power per unit area delivered by a laser pulse is 5.66×10⁻¹⁷ Watt m⁻².

Explanation:

The power per unit area is given as,

$P=\frac{E}{At}$      (1)

Where,

P=power per unit area

E=energy of the laser pulse

A=area of the spot=πr²

t=time during which the laser action occurs

From the question we have,

E=4×10³Joule

t=10⁹second

The radius of the spot(r)=1.5×10⁵m

The area of the spot is given as,

$A=\pi\times (1.5\times 10^5)^2=3.14\times 2.25\times 10^1^0$

$A=7.065\times 10^1^0m^2$      (2)

By substituting the required values in equation (1) we get;

$P=\frac{4\times 10^3}{7.065\times 10^1^0\times 10^9}=0.566\times 10^-^1^6$

$P=5.66\times 10^-^1^7 Watt/m^2$

Hence, the power per unit area delivered by a laser pulse is 5.66×10⁻¹⁷ Watt m⁻².