10cm
12cm
50cm
60cm
Correct answer is B
Lens formula:
\(\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}\)
where f, d\(_o\) and d\(_i\) are the focal length, object distance and image distance respectively.
The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths.
⇒ \(\frac{-1}{30} = \frac{1}{d_o} + \frac{1}{20}\)
\(\frac{1}{d_o} = \frac{-1}{30} - \frac{1}{20}\)
\(\frac{1}{d_o} = \frac{-2 + -3}{60}\)
→ \frac{-5}{60}\) = \frac{-1}{12}\)
\(d_o = - 12 cm\)
The object distance -12cm = 12cm on the other side of the lens.
Which of the following is not a function of the West African Development Bank?
Promotion of both private and public investments in member states
Financing and executing projects in member states
Promotion of social development of member states
Harmonization of oil prices to the advantage of member states
Correct answer is B
The functions of the West African Development Bank does not include financing and executing projects in member states.
The refractive index of a material is 1.5. Calculate the critical angle at the glass-air interface
19o
21o
39o
42o
Correct answer is D
Sin C = \(\frac{1}{\eta} = \frac{1}{1.5} = 0.6667\)
C = sin\(^{-1}\) 0.6667
= 42°
One of the reasons why government may erect a trade barrier is to
Control foreign currencies
Protect infant industries
Promote importation
Diverisify the economy
Correct answer is B
Barriers to trade are often used as protection of infant and local industries. Their stated purpose is to shield or advance particular industries or segments of an economy. These barriers include tariffs.
Balance of payments problem can be corrected through
Increasing foreign reserves
Increasing domestic borrowing
Import promotion strategies
Export promotion strategies
Correct answer is D
Balance of payment problems can be corrected by Export Promotion strategy. This strategies are aimed at promoting the industries that have potential for developing and competing with foreign rivals.