# 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

Arial magnification,

Linear magnifications, ml

**Question: 2.10**

State the number of significant figures in the following:

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.