Grace the dog and Cadbury the cat at f2.8 aperture mode shots in my bedroom, a 35 mm DX lens because of the crop factor appears like an old film 52mm lens, the film normal lens was the 50mm which approximated the field of view of normal human vision. The 35mm lens seems razor sharp, but it has one other quality that suits it for pet pix or people portraits, by going to aperture mode and shooting at f2.8 or even down to f1.8, you can throw the background out of focus and keep the main subject sharp. the otherwise excellent kit lens with the D3100, 18-55mm f3.5-f4.5 lens, cannot do that.
SOUNDS COMPLICATED BUT it really isn’t and the rewards are photos with more impact by making the depth of field shallow and selective. Try it out.