added run time parameter

video.py

@@ -12,5 +12,5 @@ class Slide1(Scene):
         image_with_raytracing.set_y(0)
         image_with_raytracing.scale_to_fit_width(1)
 
-        self.play(FadeIn(image_no_raytracing, image_with_raytracing))
+        self.play(FadeIn(image_no_raytracing, image_with_raytracing), run_time=3)