Phyisics, laws of refraction PLEASE HELP

[Alien_poo]

(SEE ATTACHED PROJECT) Ok, I have some light (the blue line on the right) coming through a substance, hitting another substance, and refracted at a certain angle (the blue line on the left). You enter the density of the second material in the text box, and choose the angle the light is hitting the second material (with the scroll-bar). Now the blue line on the left is suppose to move with the blue line on the right. Which is working... but not the right way! Proof: if you put the second material's density to 1, the light should NOT be refracted, but if you look at the blue line, when you come to an angle of 60 or so, it does start being refracted! And at an angle of like 65 the app gives me an error. PLEASE help me find what the problem is, I am getting desperate, this school project is for tomorrow.

[mendhak]

Well, the value you're getting for

When dividing, the value in the denominator is:

-2.75579550151111E-02

Which I guess is too small, and producing a really large value to be squared.

[Alien_poo]

how can I fix that?

[mendhak]

Option Explicit
Dim N2 As Single
Dim AngleI As Integer
Dim AngleR As Double
Dim Reponse As Integer
Dim X As Double
 
Private Sub Command1_Click()
    End
End Sub
 
Private Sub Command2_Click()
    Text1.Text = ""
End Sub
 
Private Sub HScroll1_Change()
    If Val(Text1.Text) <= 0 Then
        Reponse = MsgBox("Veuillez entrez un indice de refraction plus grand que 0", vbOKOnly + vbCritical, "Indice de refraction impossible")
        Exit Sub
    End If
    
    Line2.Visible = True
    Line3.Visible = True
    AngleI = HScroll1.Value
    N2 = Val(Text1.Text)
    
    Line2.Y2 = 2000 - (1500 * Sin(AngleI * 3.141592 / 180))
    Line2.X2 = 3000 + (1500 * Cos(AngleI * 3.141592 / 180))
    
    X = (AngleI * 3.14592 / 180) / N2
    'AngleR = Atn(X / Sqr(-X * X + 1))
    AngleR = ArcSin(X)
    
    Line3.Y2 = 2000 + (1500 * Sin(AngleR))
    Line3.X2 = 3000 - (1500 * Cos(AngleR))
End Sub
 
Function ArcSin(X As Double) As Double
    X = CDbl(X)
    'ArcSin = (Atn(X / Sqr(-X * X + 1)))
    ArcSin = (Atn(X / ((-X * X + 1) * (-X * X + 1))))  '[b]I changed this[/b]
End Function

Is this acceptable?

[jemidiah]

Actually, it's being square-rooted

It's producing a negative value which, of course, can't be square rooted without producing an imaginary number. Inverse tangent may actually be able to use imaginary numbers (I'm not sure on that, though), but VB doesn't like them. What is the formula you've been supplied with?

Edit: It just hit me why that's not working: arcsin has a domain of -1 to 1 because that's the range of sin, so passing it a value of x greater than 1 or less than -1 will cause an error like that. Again, I'd have to see the formula to help.

[alkatran]

if I remember right, when you get an error when tryingto calculate that, it means the light was... absorbed, or travelling parrallel to the surface, or something like that... just use error checking