5 REM **** PROGRAM RBOWBEAM ****
10 DIM X(10), Y(10), TH(10)
20 PI = 3.141593: DRC = PI / 180
30 N = 1.33
40 SCRFAC = 3 / 4: X(1) = -4.5
50 INPUT "FOR PRIMARY BOW TYPE 1, FOR SECONDARY, TYPE 2  ", NBOW
60 IF NBOW = 1 THEN SN = 1 ELSE SN = -1
70 CLS : SCREEN 12
80 WINDOW (-5, -5 * SCRFAC)-(1.5, 1.5 * SCRFAC)
90 CIRCLE (0, 0), 1: REM RAINDROP
100 FOR I = 3 TO 90 STEP 3
110 TH(1) = I * DRC * SN: REM ANGLE OF INCIDENCE
120 Y(1) = SIN(TH(1))
130 QQ = SIN(TH(1)) / N
140 R = SN * ATN(SQR(1 / (1 - QQ ^ 2) - 1))
200 FOR J = 2 TO 3 + NBOW
210 TH(J) = TH(J - 1) + (PI - 2 * R)
230 Y(J) = SIN(TH(J - 1))
240 X(J) = -COS(TH(J - 1))
250 NEXT J
300 DEV = (PI - 2 * (TH(1) - R) - NBOW * (PI - 2 * R))
310 X(4 + NBOW) = X(3 + NBOW) + DX - COS(2 * PI + DEV) * 3
320 Y(4 + NBOW) = Y(3 + NBOW) + DY - SIN(2 * PI + DEV) * 3
400 FOR J = 1 TO 3 + NBOW
FOR KK = 1 TO 3000
XX = KK * (X(J + 1) - X(J)) / 3000 + X(J)
YY = KK * (Y(J + 1) - Y(J)) / 3000 + Y(J)
PSET (XX, YY), J
NEXT KK
410 REM LINE (X(J), Y(J))-(X(J + 1), Y(J + 1)), J
420 NEXT J
LOCATE 1, 26: PRINT "               "
LOCATE 2, 26: PRINT "               "
LOCATE 2, 36: PRINT "               "
LOCATE 1, 1: PRINT "ANGLE OF INCIDENCE     ="; I
LOCATE 2, 1: PRINT "ANGLE OF REFRACTION    ="; R / DRC
LOCATE 3, 1: PRINT "DEVIATION ANGLE OF RAY ="; (180 + 2 * I - 4 * R / DRC)

WHILE INKEY$ = "": WEND
490 NEXT I
WHILE INKEY$ = "": WEND