Question 8 The figure below shows a ripple tank which is used to study the behavior of water waves. Water waves
are produced in the tank. The shadow of the waves is projected onto the screen below the tank. A clear
view of the screen is also shown to the right of the ripple tank. What is the approximate wavelength of
the waves as seen on the screen?
metre ruler
SCREEN
lamp
dipper dips in and out of the
water producing ripples
to signal generator
o cm
water
screen
90 cm
shadows cast by ripples
metre ruler
A. 10 cm
B. 11 cm
C. 98 cm
D. 720 cm
Justify your

it would be c. predictability

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

3. dark matter

empty space could also be a simple vacuum