Which of the main parts of an optical fibre has a higher value of refractiv index?

Which of the following is true about the value of refractive index of quartz glass?

A thin glass (refractie index = 1.5) lens has optical power of -5 D in air.Its optical power in a liquuid of refractive index 1.6 will be

Which of the two, an ammeter or a milliammeter, has a higher resistance and why?

Which has highest pk_a value?

Which one of the following phenols has the highest pK_a Value ?

Which material has least value of resistivity.

Which of the following has higher value : BOD or COD?