# Animate doesn't work

I'm trying to animate plot:
a, A, B and C are constants. So I wrote the following script:

a:=1;
E1:=1.6*10^(-19);
E2:=1.6*10^(-19);
E3:=1.6*10^(-19);
h = 6.63*10^-34;
f[x_,t_] = (Sqrt[a]/2) (((10/16) Sin[Pi (x/a)])/E^(I (E1 (t/h)))
- ((5/16) Sin[3 Pi (x/a)])/E^(I (E2 (t/h)))
+ ((1/16) Sin[5 Pi (x/a)])/E^(I (E3 (t/h))));
Animate[Plot[f[x,t],{x,0,a}, Filling ->Bottom, AxesLabel ->Automatic],
{t,0,100, 1},AnimationRunning->False]


I get empty graph. Okay, maybe my function is not right, so I've tried f[x_,t_] = Sin(x*t); And again, the graph is empty. What am I doing wrong?

• Don’t use _ in the animate Dec 21, 2017 at 18:03
• you need to define h and also as @CarlWoll pointed, use f[x,t] inside Plot. Also make sure f[x,t] returns real value. Dec 21, 2017 at 18:08
• @Sumit h isn't defined as Planck constant? Dec 21, 2017 at 18:10
• @Russiancold you should define the Planck constant as hbar = UnitConvert@Quantity[None, "PlanckConstant"] if you want to use its numerical value. Dec 21, 2017 at 18:18
• h isn't defined as Planck constant? Mathematica does not know that h is supposed to be Planck constant. You can do ?h to find out. Also, if it were, Mathematica uses UpperCase for such things. Dec 21, 2017 at 18:18

Assuming that you are trying to see the superposition of three different wavefunctions here is your answer.

a = 1;
E1 = 1.6*10^(-19);
E2 = 2.6*10^(-19);
E3 = 3.6*10^(-19);
h =  6.63*10^-34;
f[x_, t_] := (Sqrt[a]/ 2) (((10/16) Sin[Pi (x/a)])/ E^(I (E1 (t/h)))
- ((5/16) Sin[3 Pi (x/a)])/ E^(I (E2 (t/h)))
+ ((1/16) Sin[5 Pi (x/a)])/E^(I (E3 (t/h))));

Animate[Plot[Abs[f[x, t]]^2, {x, 0, a}, Filling -> Bottom, PlotRange -> {0, 0.25},
AxesLabel -> Automatic], {t, 0, 100, 1}, AnimationRunning -> False]


To make sure f[x,t] returns real value I use Abs[] in the Plot. If E1=E2=E3 then you will not see any variation in time.

As José Antonio Díaz Navas pointed out, you can set the value of Planck's constant h by QuantityMagnitude@UnitConvert@Quantity[None, "PlanckConstant"] as well.

• Thanks, so comparing to my script you removed "_" and defined h to make it work, right? Why Abs[] but not Re[]? Dec 21, 2017 at 18:27
• Your function f[x,t] is complex. It is up to you to choose the real part, $\Re$ Re[], and/or the imaginary part, $\Im$ Im[], or Abs[] Dec 21, 2017 at 18:32
• That's due to my quantum mechanical habit of using $|/Psi|^2$ :) Dec 21, 2017 at 18:35
• @Sumit it's just my misunderstanding of Abs, somehow I forgot what is absolute value of complex number. Of course I need Abs but not Real part here. Dec 21, 2017 at 18:37
• @Sumit is there any way to make the animation smoother or it's caused by this certain function? I'm trying to change dt param, but animation is still rough. Btw it's psi-function) Dec 21, 2017 at 19:04