NCERT Class 11 Physics Solutions: Chapter 2-Unit and Measurement Part 6

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Question: 2.9

The photograph of a house occupies an area of 1.75 on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is. What is the linear magnification of the projector- screen arrangement?

Answer: 2.9

  • Area of the house on the slide

  • Area of the image of the house formed on the screen

Linear magnification equation

Linear Magnification Equation

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  • Arial magnification,

Linear magnifications, ml

Question: 2.10

State the number of significant figures in the following:

Rules of determining significant figures

Rules of Determining Significant Figures

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a)

b)

c)

d)

e)

f)

Answer: 2.10

a)

The given quantity is

If the number is less than one, then all zeroes on the right of the decimal point (but left to the first non - zero) are insignificant. This means that here, two zeroes after the decimal are not significant. Hence, only 7 is a significant figure in this quantity.

b)

The given quantity is

Here, the power of 10 is irrelevant for the determination of significant figures. Hence, all digits i.e., 2, 6 and 4 are significant figures.

c)

The given quantity is

For a number with decimals, the trailing zeroes are significant. Hence, besides digits 2, 3 and 7, 0 that appears after the decimal point is also a significant figure.

d)

The given quantity is

For a number with decimals, the trailing zeroes are significant. Hence, all four digits appearing in the given quantity are significant figures.

e)

The given quantity is.

All zeroes between two non – zero digits are always significant.

f)

The given quantity is

If the number is less than one, then the zeroes on the right of the decimal point (but left to the first non - zero) are insignificant. Hence, all three zeroes appearing before 6 are not significant figures. All zeroes between two non – zero digits are always significant. Hence, the remaining four digits are significant figures.