Question

An oscilloscope screen displays a line inclined at ${45}^o.$ Its $Y-input$ is a sine wave of frequency $f$ then the $X-input$ should be

• A. sine wave of frequency $f$ and $0^o$ phase shift with the $Y-input$
• B. sine wave of frequency $f$ and ${45}^o$ phase shift with the $Y-input$
• C. sine wave of frequency $f$ and $0^o$ phase shift with the $Y-input$
• D. saw-tooth wave of frequency $f$

Answer 1

The correct option is A sine wave of frequency $f$ and $0^o$ phase shift with the $Y-input$

When we apply sinusoidal waves on both $XXandYY$ plates, then pattern is Lissajous figure.
When phase difference is zero between them then,
We get a stright line inclined at ${45}^o$. In other cases ellipse is formed.
Since oscilloscope displays a line
$\Rightarrow \varphi =0$ and frequency is same for $X$ and $Y$ and inclination is ${45}^o.$
$\Rightarrow V_X=V_Y$.