10.1 Two small spheres, A and B, made of pure zinc are at rest 0.1 m apart on a wooden table - NSC Physical Sciences - Question 10 - 2023 - Paper 1

To determine if the ultraviolet light will eject electrons from sphere B, we can use the photoelectric equation:

$E = hf$

Where:

• $E$ is the energy of the photons
• $h$ is Planck’s constant ($6.63 × 10^{-34}$ Js)
• $f$ is the frequency of the ultraviolet light ($2.8 × 10^{16}$ Hz)

Calculating the energy:

$E = (6.63 × 10^{-34} ext{ Js})(2.8 × 10^{16} ext{ Hz}) = 1.86 × 10^{-17} ext{ J}$

Since the energy of the ultraviolet light (1.86 × 10^-17 J) is greater than the work function of zinc (6.63 × 10^-19 J), it will be sufficient to eject electrons from sphere B.

To calculate the minimum number of photons required to exert a force on sphere A, we first determine the energy needed to overcome the force:

The charge on sphere A is $q = -5.4 × 10^{-6} C$.

Using the force equation, F = rac{k imes |q_1| imes |q_2|}{r^2} we can calculate.

Rearranging gives us:

$E = F imes d$

Where:

• $F = 0.027 ext{ N}$
• $d = 0.1 ext{ m}$

Thus, the energy:

$E = 0.027 ext{ N} imes 0.1 ext{ m} = 0.00027 ext{ J}$

Now, the energy per photon is $E_{photon} = 1.86 × 10^{-17} ext{ J}$.

Therefore, the minimum number of photons, $n$, is:

n = rac{E}{E_{photon}} = rac{0.00027 ext{ J}}{1.86 × 10^{-17} ext{ J}}

Calculating gives:

The type of line spectrum observed is an absorption spectrum.

The absorption spectrum consists of a continuous spectrum of light with dark lines superimposed on it. These dark lines correspond to specific wavelengths of light that have been absorbed by the gas, indicating the presence of particular elements.

The type of spectrum observed is consistent with DIAGRAM A, as it shows energy transitions that would lead to absorption of specific wavelengths of light.