NEET 2019 P1 Question Paper - PYQ Mock Test

Two similar thin equi-convex lenses, of focal length $f$ each, are kept coaxially in contact with each other such that the focal length of the combination is $F_1$. When the space between the two lenses is filled with glycerin (which has the same refractive index ($\mu =1.5$) as that of glass) then the equivalent focal length is $F_2$. The ratio $F_1:F_2$ will be:

Increase in temperature of a gas filled in a container would lead to:

An electron is accelerated through a potential difference of $10,000\text{V}$. Its de Broglie wavelength is, (nearly): ($m_e=9\times 10^{-31}\text{kg}$)

A copper rod of $88\text{cm}$ and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is: (${\alpha }_{Cu}=1.7\times 10^{-5}{\text{K}}^{-1}$ and ${\alpha }_{Al}=2.2\times 10^{-5}{\text{K}}^{-1}$)

Pick the wrong answer in the context with rainbow.