whenever i use individual value of time (Tv) the output function (F) giving right value but using time in the form of loop ,output function gives wrong result for all.How to fix this ?

clc

clear all

c1 = 3.742*10.^8;

c2 = 1.43878*10.^4;

sigma = 5.67*10.^-8;

lamda_1 = 8;

lamda_2 = 13;

Tv = -10:5:30;

F = zeros(size(Tv));

count = 1;

for T=Tv

fun = @(lambda) c1./(lambda.^5.*(exp(c2./(lambda * T+273)))-1);

F(count) = integral(fun,lamda_1,lamda_2)./(sigma.*(T+273)^4)

plot(T, F(count), '+', 'MarkerSize', 10, 'LineWidth', 2)

hold on

grid

count = count + 1;

end

xlabel('Temperature')

ylabel('Fraction in atmospheric window)')

title('Fraction of the radiation emitted in the atmospheric window as a function of temperature')

legend('T=-10','T=-5','T=0','T=5','T=10','T=15','T=20','T=25','T=30')

hold off

Answer 1

[Alan Stevens]

You missed a set of brackets connecting TV to 273.

c1 = 3.742*10.^8;
c2 = 1.43878*10.^4;
sigma = 5.67*10.^-8;
lamda_1 = 8;
lamda_2 = 13;
Tv = -10:5:30;
F = zeros(size(Tv));
count = 1;
for T=Tv
fun = @(lambda) c1./(lambda.^5.*(exp(c2./(lambda *(T+273))))-1); %%%%%%%
F(count) = integral(fun,lamda_1,lamda_2)./(sigma.*(T+273)^4);
plot(T, F(count), '+', 'MarkerSize', 10, 'LineWidth', 2)
hold on

count = count + 1;
end
grid
xlabel('Temperature')
ylabel('Fraction in atmospheric window)')
title('Fraction of the radiation emitted in the atmospheric window as a function of temperature')
legend('T=-10','T=-5','T=0','T=5','T=10','T=15','T=20','T=25','T=30')
hold off

[Sarvjeet Singh]

How to get a staright line in graph rather than + sign

[Alan Stevens]

Delete the '+','MarkerSize',10, from the plot command.

[Sarvjeet Singh]

now the graph is totally blank

[Alan Stevens]

Try this

c1 = 3.742*10.^8;
c2 = 1.43878*10.^4;
sigma = 5.67*10.^-8;
lamda_1 = 8;
lamda_2 = 13;
Tv = -10:5:30;
F = zeros(size(Tv));
count = 1;
for T=Tv
fun = @(lambda) c1./(lambda.^5.*(exp(c2./(lambda *(T+273))))-1); %%%%%%%
F(count) = integral(fun,lamda_1,lamda_2)./(sigma.*(T+273)^4);
plot(T, F(count),'+')
hold on
count = count + 1;
end
plot(Tv,F)
grid
xlabel('Temperature')
ylabel('Fraction in atmospheric window)')
title('Fraction of the radiation emitted in the atmospheric window as a function of temperature')
legend('T=-10','T=-5','T=0','T=5','T=10','T=15','T=20','T=25','T=30')
hold off

It results in

[Alan Stevens]

Or, if you don't want the crosses at all:

c1 = 3.742*10.^8;
c2 = 1.43878*10.^4;
sigma = 5.67*10.^-8;
lamda_1 = 8;
lamda_2 = 13;
Tv = -10:30;
F = zeros(size(Tv));
count = 1;
for T=Tv
fun = @(lambda) c1./(lambda.^5.*(exp(c2./(lambda *(T+273))))-1); 
F(count) = integral(fun,lamda_1,lamda_2)./(sigma.*(T+273)^4);
count = count + 1;
end
plot(Tv,F)
grid
xlabel('Temperature')
ylabel('Fraction in atmospheric window)')
title('Fraction of the radiation emitted in the atmospheric window as a function of temperature')

[Sarvjeet Singh]

thank you