Two tuning forks X and Y vibrate at 256 Hz and 512 Hz respectively. Both are struck with the same force. Which statement about the sounds they produce is correct?
a) X is shriller than Y because it has higher frequency.
b) Y is graver than X because it has larger amplitude.
c) Y is shriller than X because it has higher frequency.
d) Both produce sounds of equal pitch because the amplitude of vibration is the same.