# IB DP Physics Unit 1. Measurements and uncertainties Paper 1

Question

What is the order of magnitude of the wavelength of visible light?
A. 10-10 m
B. 10-7 m
C. 10-4 m
D. 10-1 m

Ans

$B$

Visible light which is detectable by the human eye consists of wavelength ranging from approximately $780nm\left ( 7.80\times 10^{-7}m \right )-390nm\left ( 3.90\times 10^{-7}m\right )$ . So, the wavelength of light visible to the eye is of the order of   $10^{-7}m$

### Question

Which quantity has the same units as those for energy stored per unit volume?

A Density

B Force

C Momentum

D Pressure

Ans: D

$$\frac{Energy}{Volume}=\frac{work}{area\times length}=\frac{force \times distance}{area\times length}$$

$$=\frac{MLT^{-2}\times L}{L^2\times L}=\left [ ML^{-1}T^{-2} \right ]=pressure$$

### Question

Which is a unit of force?

A. J m

B. J m–1

C. J m s–1

D. J m–1 s

### Markscheme

B

A joule per meter (J/m) is a metric unit of force. In mechanics, a joule is defined as the work done by a force of one newton acting to move an object through a distance of one meter in the direction in which the force is applied (1 J = 1 N·m). Therefore, joule per meter is equal to newton.

### Question

What is the best estimate for the diameter of a helium nucleus?

A. 10–21 m

B. 10–18 m

C. 10–15 m

D. 10–10 m

Markscheme

### C

The size of the helium nucleus is about 1 fermi, or 1 fm, which is equivalent to 10-15 m. The atom is about 100,000 times bigger than the nucleus, with an atom size of about 105 fm or 10-10 m.

### Question

How many significant figures are there in the number 0.0450?

A. 2

B. 3

C. 4

D. 5

Markscheme

B

The first one being that all non-zero numbers are significant. With a 4 and a 5 in the number, we know there are at least 2 significant digits.

Lastly , is that a trailing zero after a decimal is significant. So the 450 is significant. The  zeros in front of the decimal are irrelevant.

Therefore, there are 3 significant digits in this number. Please visit below link for more details

IB Physics Unit 1. Measurements and uncertainties- 1.1 Measurements in physics: Study Notes

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