After the first half-life, then ½ (5.12 × 1020) = 2.56 × 1020 will have decayed.
The second half-life, then ½ (2.56 × 1020) = 1.28 × 1020 will have decayed.
The total number of decayed atoms = (2.56 + 1.28) × 1020 = 3.84 × 1020 atoms.
Mutiso answered the question on October 17, 2018 at 10:10
- An isotope has a half-life of 576 hours. Complete the following table and show how mass varies with time from an initial mass of 1280...(Solved)
An isotope has a half-life of 576 hours. Complete the following table and show how mass varies with time from an initial mass of 1280 g?
Time (hrs)----576--1152--1728---2304
Mass (g)-------640--x------y-----z
Date posted: October 17, 2018. Answers (1)
- The half-life of a sample of a radioactive substance is 98 minutes. How long does it take for the activity of the sample to reduce...(Solved)
The half-life of a sample of a radioactive substance is 98 minutes. How long does it take for the activity of the sample to reduce to 1/16th of the original value?
Date posted: October 17, 2018. Answers (1)
- State the law of radioactive decay(Solved)
State the law of radioactive decay
Date posted: October 17, 2018. Answers (1)
- Explain ways of detecting nuclear radiation(Solved)
Explain ways of detecting nuclear radiation.
Date posted: October 17, 2018. Answers (1)
- Properties of radioactive emissions(Solved)
Properties of radioactive emissions
Date posted: October 17, 2018. Answers (1)
- Sodium has a work function of 2.0 e: Calculate (a) The maximum energy and velocity of the emitted electrons when sodium is Illuminated by...(Solved)
Sodium has a work function of 2.0 e: Calculate
(a) The maximum energy and velocity of the emitted electrons when sodium is Illuminated by a radiation of wavelength 150 nm.
(b) Determine the least frequency of radiation by which electrons are emitted. (Take ‘h’ = 6.626 × 10-34 Js, e = 1.6 × 10-19, c = 3.0 × 108 m/s and mass of electron = 9.1 × 10-31 kg).
Date posted: October 17, 2018. Answers (1)
- The threshold frequency for lithium is 5.5 × 1014 Hz. Calculate the work function for lithium. (Take ‘h’ = 6.626 × 10-34 Js)(Solved)
The threshold frequency for lithium is 5.5 × 1014 Hz. Calculate the work function for lithium. (Take ‘h’ = 6.626 × 10-34 Js)
Date posted: October 17, 2018. Answers (1)
- The work function of tungsten is 4.52 e V. Find the cut-off potential for photoelectrons when a tungsten surface is illuminated with radiation of wavelength...(Solved)
The work function of tungsten is 4.52 e V. Find the cut-off potential for photoelectrons when a tungsten surface is illuminated with radiation of wavelength 2.50 × 10-7 m. (Planck’s constant, h = 6.62 × 10-34 Js).
Date posted: October 17, 2018. Answers (1)
- The cut-off wavelength for a certain material is 3.310 × 10-7 m. What is the cut-off frequency for the material?(Solved)
The cut-off wavelength for a certain material is 3.310 × 10-7 m. What is the cut-off frequency for the material?
Date posted: October 17, 2018. Answers (1)
- What is Einstein’s photoelectric equation?(Solved)
What is Einstein’s photoelectric equation?
Date posted: October 17, 2018. Answers (1)
- Dangers of X-rays and the precautions(Solved)
Dangers of X-rays and the precautions.
Date posted: October 16, 2018. Answers (1)
- An x-ray tube operates at 60 kV and the current through it is 4.0 mA. Calculate the, (a) Number of electrons striking the target per...(Solved)
An x-ray tube operates at 60 kV and the current through it is 4.0 mA. Calculate the, (a) Number of electrons striking the target per second. (b) Speed of the electrons when they hit the target.
Date posted: October 16, 2018. Answers (1)
- Determine the energy possessed by X-rays whose frequency is 4 × 1017 Hz. (Solved)
Determine the energy possessed by X-rays whose frequency is 4 × 1017 Hz.
Date posted: October 16, 2018. Answers (1)
- Energy changes in X-Ray tube(Solved)
Energy changes in X-Ray tube
Date posted: October 16, 2018. Answers (1)
- If the time base control of the CRO is set at 10 milliseconds per cm, what is the frequency of the wave traced given wavelength...(Solved)
If the time base control of the CRO is set at 10 milliseconds per cm, what is the frequency of the wave traced given wavelength as 1.8 cm?
Date posted: October 16, 2018. Answers (1)
- Cathode Ray Oscilloscope components and functioning(Solved)
Cathode Ray Oscilloscope components and functioning.
Date posted: October 16, 2018. Answers (1)
- What are cathode rays?(Solved)
What are cathode rays?
Date posted: October 16, 2018. Answers (1)
- Illustrate domestic wiring system with aid of a diagram(Solved)
Illustrate domestic wiring system with aid of a diagram
Date posted: October 16, 2018. Answers (1)
- A house has five rooms each with a 60 W, 240 V bulb. If the bulbs are switched on from 7.00 pm to 10.30 pm,...(Solved)
A house has five rooms each with a 60 W, 240 V bulb. If the bulbs are switched on from 7.00 pm to 10.30 pm, calculate the;
(a) Power consumed per day in kWh
(b) Cost per week for lighting those rooms if it costs 90 cents per unit.
Date posted: October 16, 2018. Answers (1)
- An electric heater is made of a wire of resistance 100 ${\Omega}$ connected to a 240 V mains supply. Determine the; (a) Power rating of...(Solved)
An electric heater is made of a wire of resistance 100 ${\Omega}$ connected to a 240 V mains supply. Determine the;
(a) Power rating of the heater
(b) Current flowing in the circuit
(c) Time taken for the heater to raise the temperature of 200 g of water from 23oC to 95oC. (specific heat capacity of water = 4,200 J Kg-1K-1)
(d) Cost of using the heater for two hours a day for 30 days if the power company charges Ksh 5.00 per kWh.
Date posted: October 16, 2018. Answers (1)