(1) A. Particle P is forced to vibrate under the driving force of the wave source, and its vibration period is equal to that of the wave source, so the vibration period of particle P is t. The point velocity is different from the wave velocity, so its maximum velocity cannot be determined. So, A is wrong.

B when the wavelength is λ=vT and x = 5T2 = 52λ, the vibration at point P is always opposite to that of the wave source. When the velocity direction of particle P is negative along the Y axis, the velocity direction of particle vibration at the wave source at that moment is positive along the Y axis. Therefore, B is correct.

C, the direction in which the particle P starts to vibrate is the same as the direction in which the wave source starts to vibrate, that is, along the positive direction of the Y axis. So, C is correct.

D, the particle P does not follow the wave along the positive direction of the X axis, but simply vibrates near its equilibrium position. So, d is wrong.

So choose BC?

(2) According to the geometric relationship, what is the refraction angle? r=30

The refractive index of light in this medium is n = sinisinr = sin45 sin30 = 2?

The propagation speed of light in this medium v=cn=2. 1× 108? M/s

A:

(1) BC;

(2) The refractive index of light in this medium is 2, and the propagation speed is 2. 1× 108? Postgraduate students.