Update app.py

app.py

@@ -407,7 +407,11 @@ def create_demo():
             ],
             [
                 "./examples/18.png",
-                "Consider a string of \(L=2.00 \mathrm{~m}\) attached to an adjustable-frequency string vibrator as shown in the figure <image_start>[problem_image_1]<image_end>. The waves produced by the vibrator travel down the string and are reflected by the fixed boundary condition at the pulley. The string, which has a linear mass density of \(\mu=0.006 \mathrm{~kg} / \mathrm{m}\), is passed over a frictionless pulley of a negligible mass, and the tension is provided by a 2.00-kg hanging mass.\n(a) What is the velocity of the waves on the string?\n(b) Draw a sketch of the first three normal modes of the standing waves that can be produced on the string and label each with the wavelength.\n(c) List the frequencies that the string vibrator must be tuned to in order to produce the first three normal modes of the standing waves.",
+                "Consider a string of \(L=2.00 \mathrm{~m}\) attached to an adjustable-frequency string vibrator as shown in the figure. The waves produced by the vibrator travel down the string and are reflected by the fixed boundary condition at the pulley. The string, which has a linear mass density of \(\mu=0.006 \mathrm{~kg} / \mathrm{m}\), is passed over a frictionless pulley of a negligible mass, and the tension is provided by a 2.00-kg hanging mass.\n(a) What is the velocity of the waves on the string?\n(b) Draw a sketch of the first three normal modes of the standing waves that can be produced on the string and label each with the wavelength.\n(c) List the frequencies that the string vibrator must be tuned to in order to produce the first three normal modes of the standing waves.",
+            ],
+            [
+                "./examples/19.png",
+                "The adventure starts at the green square. By following travel leftward 1 step, where do you conclude?",
             ],
         ]