**Answer:**

**Explanation:**

Given:

- original frequency of the wave,

- velocity of the blood stream moving away,

__Doppler shift is given as:__

where:

s = velocity of ultrasound in blood =

velocity of sound source towards the observer

velocity of the observer away from the source

Therefore the shift in frequency:

**Answer:**

Frequency and wavelength are inversely proportional to each other. The wave with the greatest frequency has the shortest wavelength. Twice the frequency means one-half the wavelength. For this reason, the wavelength ratio is the inverse of the frequency ratio.

**Answer:**

19 cm

**Explanation:**

inner radius, a = 16 cm, C = 113 p F = 113 x 10^-12 F

Let b cm be the radius of outer sphere.

The formula of capacitance of spherical capacitor is given by

C = 4π∈0 a b / (b - a)

a b / ( b - a) = C / 4π∈0

a b / ( b - a ) = 113 x 10^-12 x 9 x 10^9

a b / ( b - a ) = 1.017

16 x 10^-2 x b x 10^-2 = 1.017( b - 16) x 10^-2

0.16 b = 1.017 b - 16.272

0.857 b = 16.272

b = 19 cm

**Answer:**

The Fluorescent lamp is most efficient

**Explanation:**

66.7 lumens/watt

Fluorescent was always the most efficient vs. incandescent or halogen gas envelope

This question needs some updating as LED lamps now beat fluorescents in life expectancy and lumens/watt.