REGENTS PHYSICS RIPPLE TANK MR. GAGNON LABS

I.

When a ray reflects off a surface, the angle of incidence is the angle between the incoming (incident) ray and the normal. The angle of reflection is the angle between the outgoing (reflected) ray and the normal. The normal is a line that is perpendicular to the surface. The fronts are perpendicular to the rays.

1) Set up the ripple tank with the yellow triangular reflector as shown. 2) Put water in the tank up to (but not over) the reflector. 3) Turn the wave knob on and off quickly so you make just a few . 4) Observe the reflections and note their direction 5) Construct a normal line (a dotted line perpendicular to the boundary line) on the paper 6) Draw a ray representing the incoming waves (see diagram above) 7) Draw a ray representing the reflected waves 8) Measure the incident and reflected angles II.

As a wave passes from one medium to another, it changes speed. If it slows down, the wave will bend toward the normal as shown in the figure. This bending is called refraction.

1) Set up Ripple Tank the same way as Reflection except just barely submerge the yellow triangle. The water over the yellow triangle makes a shallow end for the waves to go into. 2) Turn wave maker on a low frequency. Draw a line along the boundary (edge of yellow triangle) and construct a normal. Construct an incoming ray so that it hits the boundary where the normal line hits the boundary 3) Construct the ray in the shallow end that represents the refracted waves. Start this ray at where the normal hits the boundary. 4) When the wave goes from the deep water to the shallow water in the triangle area, does the wave bend toward or away from the normal?

5) When the wave goes from the deep water to the shallow water in the triangle area, does the wave speed up or slow down?

III.

The purpose of this experiment is to determine how the diffraction pattern changes as the slit width and the are varied.

1) Take the triangle out of the tank and put two long straight metal reflectors about 3 cm apart in the water. Make a sketch of the wave pattern below. 2) Change the slit width both smaller and wider to answer the question: Do the waves diffract more (spread out behind the barriers more) when the opening is small or large?

3) Change the wavelength both small and large to answer the question: Do the waves diffract more (spread out behind the barriers more) when the wavelength is small or large?

4) To get the most diffraction what combination of slit width and wavelength should you use?

IV. INTERFERENCE The purpose of this experiment is to observe and sketch an interference pattern in a ripple tank 1) Remove the metal barriers or any other accessories from the tank. 2) Replace the ripple bar wavemaker with rubber attachment point sources 3) Set the frequency knob to an intermediate setting 4) Find the regions where the waves tend to cancel each other and find the regions where the waves add together to make waves with higher peaks. Make a sketch of the wave pattern on the back of this page.