Energy levels & line spectra

Electrons in a fluorescent tube are accelerated from rest by a potential difference of 130 V.

Calculate the maximum speed of an electron that is accelerated from rest by this potential difference.

Explain why the average speed of the electrons in the tube is much less than the maximum speed you calculated in Question 08.1.

Scientists want to replace the mercury in fluorescent tubes with substance X.

Figure 12 is an emission spectrum for X.

White light consists of the whole range of visible wavelengths from 380 nm to 700 nm

Explain, with reference to Figure 12, whether white light can be produced by a fluorescent tube that uses X.

Figure 12 shows a maximum intensity peak that occurs at wavelength λ_peak.

Calculate, in eV, the energy change of an atom that produces a photon with a

The diagram shows some of the energy levels for a hydrogen atom.

Photons of energy 12.74 eV excite hydrogen atoms that are all initially in the ground state (n = 1).

How many different photon frequencies are emitted as the atoms return to their

Three energy levels for an atom are shown.

Energy change E₁ leads to the emission of a photon of wavelength λ₁. Energy change E₂ leads to the emission of a photon of wavelength λ₂.

Two stable isotopes of helium are 42He and 32He.

An atom of 42He is produced in a rock that contains uranium. It is produced following 238 the radioactive decay of a 92U atom. The decay also creates an atom of thorium (Th).

238 Write an equation for the decay of 92U.

238

A 32He nucleus can be produced by the decay of a tritium nucleus 31H.

State and explain which exchange particle is responsible for this decay.

Helium was discovered by analysing the light in the absorption spectrum of the Sun.

Figure 1 shows the positions of the brightest lines, labelled A to F, in the emission spectrum of helium. The brightest lines in the emission spectra of sodium and hydrogen are also shown.

Before helium was identified, some scientists suggested that the lines of the helium spectrum seen in the absorption spectrum of the Sun were due to the presence of sodium and hydrogen.

Discuss, with reference to the lines A to F in Figure 1, the evidence for and against this suggestion.

Calculate, in eV, the change in energy level responsible for the spectral line labelled in Figure 1.

Explain, with reference to the processes within an atom, the difference between an emission spectrum and an absorption spectrum.

The diagram shows the three lowest energy levels for an atom. The energy levels have been drawn to scale.

Transitions of electrons between these energy levels produce photons of the following frequencies:

What is the difference in energy between the ground state and energy level 1 ?

The diagram shows an energy - level diagram for a hydrogen atom.

Electrons, each having a kinetic energy of 2.0 × 10⁻¹⁸ J, collide with atoms of hydrogen in their ground state. Photons are emitted when the atoms de-excite.

How many different wavelengths can be observed with incident electrons of this energy?

Electrons with energy 13.0 eV collide with atoms of hydrogen in their ground state.

What is the number of different wavelengths of electromagnetic radiation that could be emitted when the atoms de-excite?