Which of the following statements are correct? i. land and sea breezes are natural convection currents. ii. convection may occur in liquids or gasses but not in solids. iii. the vacuum in a thermos flask prevents heat loss due to convection only.
A light wave of frequency 5 x 10\(^{14}\)Hz moves through water which has a refractive index of \(\frac{4}{3}\). Calculate the wavelength in water if the velocity of light in air is 3 x 10\(^8\)ms\(^{-1}\)
A wave disturbance travelling in air enters a medium in which its velocity is less than that in air. Which of the following statements is true about the wave medium?
A.
both the frequency of the wave and the wavelength are decreased
B.
the frequency of the wave is decreased while the wavelength is increased
C.
the frequency of the wave is unaltered while the wavelength is decreased
D.
the frequency of the wave is decreased while the wavelength is unaltered
An object which is 3cm high is placed vertically 10cm in front of a concave mirror. If this object produces an image 40cm from the mirror, the height of the image is
