The power of a lens is  + 2D . Then its focal length is ________ and the kind of the lens is ________.

$\text{P}=\text{+2D}$ 

$\text{Power }\left(\text{P}\right)=\frac{1}{\mathrm{f}}{\mathrm{m}}^{-1}=\frac{\text{100}}{\text{f}}{\text{\hspace{0.17em}cm}}^{-1}$

$\text{f}=\frac{\text{100}\text{cm}}{\text{P}}=\frac{\text{100}\text{cm}}{\text{2}}=\text{50}\text{cm}$

$\text{f}=\text{50 cm }$

Since the focal length is positive, it must be a convex lens.

Therefore, 50 cm and convex lens must be the correct answer.