Plane water waves in a ripple tank pass through a narrow gap
in a barrier.
a) draw the appearance of the waves when the gap is much
larger than the wavelength of the water waves.
b) draw the appearance of the waves when the gap is the
same size as the wavelength of the water waves.
explain why designers must choose the size of a harbour
entrance carefully if boats moored there are to be in
calm water.

a longitudinal wave moves energy that is to the direction of the wave’s movement. - true

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete

iron would move it is magnetic there is a mag field around the current in the wire

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.