When a surface is irradiated with light of wavelength \[4950\overset{\text{o}}{\mathop{\text{A}}}\,\], a photocurrent appears which vanishes if a retarding potential greater than 0.6 V is applied across the photo tube. When a different source of light is used, it is found that the critical retarding potential is changed to 1.1 V. Find the wavelength of second source.

• A. \[\text{4077}\overset{\text{o}}{\mathop{\text{A}}}\,\]
• B. \[992\overset{\text{o}}{\mathop{\text{A}}}\,\]
• C. \[628\overset{\text{o}}{\mathop{\text{A}}}\,\]
• D. \[238\overset{\text{o}}{\mathop{\text{A}}}\,\]