How to get particular level of category in magento 1.7.0.2 -

i using magento 1.7.0.2 want level of category.

for example, have categogory tree following

allcategory->mobile->samsung allcategory->clothing->men allcategory->laptop->dell 

here want access second level category means mobile,clothing,laptop

so how that

please me thank in advance.

$categories = mage::getmodel('catalog/category')                 ->getcollection()                 ->addattributetoselect('*')                 ->addisactivefilter()                 ->addattributetofilter('level',2) 

basically add ->addattributetofilter('level',2)