CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon


Question

Ultraviolet light of wavelength $$2271\;\mathop {\text{A}}\limits^o $$ from a $$100 W$$ mercury source irradiates a photo-cell made of molybdenum metal. If the stopping potential is $$-1.3 V$$, estimate the work function of the metal. How would the photo-cell respond to a high-intensity$$\left( { \sim {{10}^5}\;{\text{W}}{{\text{m}}^{{\text{ - 2}}}}} \right)$$ red light of wavelength $$6328\;\mathop {\text{A}}\limits^0 $$ produced by a He-Ne laser? $$\left( {h = 6.63 \times {{10}^{ - 34}}{\text{js,}}\;c = 3 \times {{10}^8}\;{\text{m/s}}} \right)$$


Solution

Given:
The wavelength of the light is $$2271\overset{o}A$$
The power of the laser is $$100\ W$$.
Stopping potential is $$-1.3\ V$$.

The energy required for the emission is:
$$W=\dfrac{hc}{\lambda}-eV_o$$

$$W=\dfrac{6.6\times10^{-34}\times3 \times10^8}{2271\times10^{-10}}-1.6\times10^{-19}\times1.3$$

$$W=6.64\times10^{-19}\ J$$
$$W=4.15 eV$$

The threshold frequency can be obtained as:

$$\nu_o=\dfrac Wh$$

$$\nu_o=\dfrac{6.64\times10^{-19}}{6.6\times10{-34}}$$

$$=1.006\times10^{15}Hz$$

The frequency of the red light is about $$4.74\times10^{14} Hz$$
Since the frequency of the incident light required is more than that of the red light, the photocell would respond to the incident light.

Physics
NCERT
Standard XII

Suggest Corrections
thumbs-up
 
0


similar_icon
Similar questions
View More


similar_icon
Same exercise questions
View More


similar_icon
People also searched for
View More



footer-image