GRADE 9 PRACTICE
Physics Problems: Electromagnetic waves, Grade 9
Occurrence, spectrum, application and safety of radiation.
Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.
Problem statements
The answer options are there to check against, and the walkthrough opens under each problem.
Problem #52
Electromagnetic waves and their bandsWhat concept does the description correspond to: “A propagating interconnected change in electric and magnetic fields that does not require a material medium.”?
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- \text{Description}
- \text{A propagating coupled change in electric and magnetic fields that needs no material medium.}
\text{name concepts} - ?
- \text{Let's compare approval with definition}
Electromagnetic waves arise from the accelerated movement of charges and propagate in a vacuum at the speed of light.
- \text{Let's formulate conclusion}\text{Concept} = \text{Electromagnetic wave}
Answer\text{Concept} = \text{Electromagnetic wave}
Problem #53
Electromagnetic waves and their bandsWhich concept does the description correspond to: “Radio waves, microwaves, infrared, visible, ultraviolet, x-rays and gamma radiation form the electromagnetic spectrum; the range boundaries are arbitrary.”?
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- \text{Description}
- \text{Radio waves, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays form the electromagnetic spectrum; band boundaries are conventional.}
\text{name concepts} - ?
- \text{Let's compare approval with definition}
Their common nature coexists with different interactions with matter, giving each band different applications.
- \text{Let's formulate conclusion}\text{Concept} = \text{Electromagnetic wave bands}
Answer\text{Concept} = \text{Electromagnetic wave bands}
Problem #54
Electromagnetic wavesWhat range is used for medical imaging of bones while requiring strict dose control?
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- \text{Problem}
- \text{transillumination dense fabrics}
\text{range} - ?
- \text{Need high penetrating ability}
- \text{Ionizing action requires dose control}\text{x-ray range}
Answer\text{x-ray radiation}
Problem #166
Electromagnetic waves and their bandsRadio wave frequency 100000000 Hz Find the wavelength in vacuum; c = 300000000 m/s.
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- f
- 100000000\,\text{Гц}
- c
- 300000000\,\text{м/с}
\lambda - ?
- \lambda=\frac{c}{f}\lambda=\frac{300000000}{100000000}\lambda=3\,\text{м}
Electromagnetic waves in a vacuum have the same speed.
Answer3\,\text{м}
Problem #167
Electromagnetic waves and their bandsRadio wave frequency 150000000 Hz Find the wavelength in vacuum; c = 300000000 m/s.
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- f
- 150000000\,\text{Гц}
- c
- 300000000\,\text{м/с}
\lambda - ?
- \lambda=\frac{c}{f}\lambda=\frac{300000000}{150000000}\lambda=2\,\text{м}
Electromagnetic waves in a vacuum have the same speed.
Answer2\,\text{м}
Problem #168
Electromagnetic waves and their bandsTransmitter wavelength 50 see Find the frequency in MHz, c = 300000000 m/s.
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- l
- 50\,\text{см}
- c
- 300000000\,\text{м/с}
f_{\text{МГц}} - ?
- a=\frac{l}{100}a=\frac{50}{100}a=0{,}5\,\text{м}
We convert the wavelength to meters.
- f_{\text{МГц}}=\frac{c}{a\cdot10^6}f_{\text{МГц}}=\frac{\frac{300000000}{0{,}5}}{1000000}f_{\text{МГц}}=600\,\text{МГц}
Convert the frequency from hertz to megahertz.
Answer600\,\text{МГц}
Problem #169
Electromagnetic waves and their bandsTransmitter wavelength 75 see Find the frequency in MHz, c = 300000000 m/s.
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- l
- 75\,\text{см}
- c
- 300000000\,\text{м/с}
f_{\text{МГц}} - ?
- a=\frac{l}{100}a=\frac{75}{100}a=0{,}75\,\text{м}
We convert the wavelength to meters.
- f_{\text{МГц}}=\frac{c}{a\cdot10^6}f_{\text{МГц}}=\frac{\frac{300000000}{0{,}75}}{1000000}f_{\text{МГц}}=400\,\text{МГц}
Convert the frequency from hertz to megahertz.
Answer400\,\text{МГц}
Problem #170
Electromagnetic waves and their bandsThe radio pulse returned after 12 mks. Known electronics latency 2 mks. Find the distance to the target in meters; c = 300000000 m/s.
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- t
- 12\,\text{мкс}
- d
- 2\,\text{мкс}
- c
- 300000000\,\text{м/с}
S - ?
- a=t-da=12 - 2a=10\,\text{мкс}
Subtract the electronics delay.
- T=a\cdot10^{-6}T=\frac{10}{1000000}T=0{,}00001\,\text{с}
Convert microseconds to seconds.
- S=\frac{cT}{2}S=\frac{300000000 \cdot 0{,}00001}{2}S=1500\,\text{м}
The impulse traveled its way to the target and back.
Answer1500\,\text{м}
Problem #171
Electromagnetic waves and their bandsThe radio pulse returned after 20 mks. Known electronics latency 4 mks. Find the distance to the target in meters; c = 300000000 m/s.
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- t
- 20\,\text{мкс}
- d
- 4\,\text{мкс}
- c
- 300000000\,\text{м/с}
S - ?
- a=t-da=20 - 4a=16\,\text{мкс}
Subtract the electronics delay.
- T=a\cdot10^{-6}T=\frac{16}{1000000}T=0{,}000016\,\text{с}
Convert microseconds to seconds.
- S=\frac{cT}{2}S=\frac{300000000 \cdot 0{,}000016}{2}S=2400\,\text{м}
The impulse traveled its way to the target and back.
Answer2400\,\text{м}
The theory behind these problems
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Formulas by topic
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