Answer:
the distance of image from the vertex is 45 cm and the image formed is in the glass.
Explanation:
distance of object, u = - infinity
radius of curvature, R = - 15 cm
refractive index, n = 1.5
Let the distance of image is v.
Use the formula
The image is in the glass.
Answer:
a) 3000 Hz;
b) 30 dB;
c) 1000 times.
Explanation:
a) From the human audiogram given on the figure below the black line represents the threshold for hearing the sound at each frequency. We see that the least intensity is necessary for the frequency of about 3000 Hz.
b) Using the same audiogram we see that we would need the sound of the intensity of about 30dB.
c) The least perceptible sound at 1000 Hz must be 0dB while at 100 Hz it is 30dB. These are logarithmic quantities. To transform them to the linear quantities we use the formula
where is the hearing threshold at 1000 Hz.
Therefore we have the following
is the threshold at 1000Hz and
is the threshold at 100Hz.
By exponentiating we have
Now dividing these two equations we get
Therefore, the least perceptible sound at 100Hz is 1000 times more intense than the least perceptible sound at 1000Hz.
Note: I got these values unisng the audiogram that is attached here. The one that you have might be slightly different and might yield different answers.
