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{
"metadata": {
"name": "",
"signature": "sha256:ede2b0bb266c67744fbe14f69a09ec9b5592c13400e7d0bf2db5fa598ebe9db1"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"15: Lasers"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 15.1, Page number 283"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"k=1.38*10**-23; #boltzmann constant(J/K)\n",
"T=1000; #temperature(K)\n",
"new1=7.5*10**14; \n",
"new2=4.3*10**14;\n",
"h=6.626*10**-34; #planck's constant(Js)\n",
"\n",
"#Calculation\n",
"kT=k*T;\n",
"#optical region extends from 4000 to 7000 angstrom\n",
"hnew=h*(new1-new2); \n",
"\n",
"#Result\n",
"print \"value of kT is\",kT,\"J\"\n",
"print \"value of hnew is\",hnew,\"J\"\n",
"print \"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"value of kT is 1.38e-20 J\n",
"value of hnew is 2.12032e-19 J\n",
"hnew>kT.therefore spontaneous transitions are dominant ones in optical region\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 15.2, Page number 298"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"h=6.626*10**-34; #planck's constant(Js)\n",
"c=3*10**8; #velocity of light(m/sec)\n",
"P=0.6; #power(watt)\n",
"T=30*10**-3; #time(s)\n",
"lamda=640*10**-9; #wavelength(m)\n",
"\n",
"#Calculation\n",
"E=P*T; #energy deposited(J)\n",
"n=E*lamda/(h*c); #number of photons in each pulse\n",
"\n",
"#Result\n",
"print \"energy deposited is\",E,\"J\"\n",
"print \"number of photons in each pulse is\",round(n/10**16,1),\"*10**16\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"energy deposited is 0.018 J\n",
"number of photons in each pulse is 5.8 *10**16\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 15.3, Page number 298"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"lamda=5000*10**-10; #wavelength(m)\n",
"f=0.2; #focal length(m)\n",
"a=0.009; #radius of aperture(m)\n",
"P=2.5*10**-3; #power(W)\n",
"\n",
"#Calculation\n",
"A=math.pi*lamda**2*f**2/a**2; #area of spot at focal plane(m**2)\n",
"I=P/A; #intensity at focus(W/m**2)\n",
"\n",
"#Result\n",
"print \"area of spot at focal plane is\",round(A*10**10,2),\"*10**-10 m**2\"\n",
"print \"intensity at focus is\",round(I/10**6,3),\"*10**6 W/m**2\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"area of spot at focal plane is 3.88 *10**-10 m**2\n",
"intensity at focus is 6.446 *10**6 W/m**2\n"
]
}
],
"prompt_number": 11
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 15.4, Page number 298"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"lamda=693*10**-9; #wavelength(m)\n",
"D=3*10**-3; #diameter of mirror(m)\n",
"d=300*10**3; #distance from earth(m)\n",
"\n",
"#Calculation\n",
"delta_theta=1.22*lamda/D; #angular spread(rad)\n",
"a=delta_theta*d; #diameter of beam on satellite(m)\n",
"\n",
"#Result\n",
"print \"angular spread is\",round(delta_theta*10**4,2),\"*10**-4 rad\"\n",
"print \"diameter of beam on satellite is\",round(a,2),\"m\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"angular spread is 2.82 *10**-4 rad\n",
"diameter of beam on satellite is 84.55 m\n"
]
}
],
"prompt_number": 15
}
],
"metadata": {}
}
]
}
|
